diff --git a/src/Http.php b/src/Http.php
index e78d71e..93bbdfd 100644
--- a/src/Http.php
+++ b/src/Http.php
@@ -7,6 +7,8 @@
 
 namespace Junaidbhura\Composer\WPProPlugins;
 
+use RuntimeException;
+
 /**
  * Http class.
  */
@@ -15,47 +17,65 @@ class Http {
 	/**
 	 * POST request.
 	 *
-	 * @param string $url Url to POST.
-	 * @param array  $args Arguments to POST.
-	 * @return mixed
+	 * @param  string                $url  URL to POST.
+	 * @param  array<string, mixed>  $args Arguments to POST.
+	 * @return string
 	 */
-	public function post( $url = '', $args = array() ) {
+	public function post( $url, $args = array() ) {
 		$curl_handle = curl_init();
 		curl_setopt( $curl_handle, CURLOPT_URL, $url );
-		curl_setopt( $curl_handle, CURLOPT_RETURNTRANSFER, 1 );
-		curl_setopt( $curl_handle, CURLOPT_FOLLOWLOCATION, true );
-		curl_setopt( $curl_handle, CURLOPT_SSL_VERIFYPEER, 0 );
-		curl_setopt( $curl_handle, CURLOPT_SSL_VERIFYHOST, 0 );
+		curl_setopt( $curl_handle, CURLOPT_SSL_VERIFYPEER, false );
+		curl_setopt( $curl_handle, CURLOPT_SSL_VERIFYHOST, false );
 		curl_setopt( $curl_handle, CURLOPT_CUSTOMREQUEST, 'POST' );
 		if ( ! empty( $args ) ) {
 			curl_setopt( $curl_handle, CURLOPT_POSTFIELDS, http_build_query( $args, '', '&' ) );
 		}
-		$response = curl_exec( $curl_handle );
-		curl_close( $curl_handle );
 
-		return $response;
+		return $this->request( $curl_handle );
 	}
 
 	/**
 	 * GET request.
 	 *
-	 * @param string $url Base URL for requeset (without params)
-	 * @param array  $args Arguments to add to request
-	 * @return mixed
+	 * @param  string                $url  URL to GET (without params).
+	 * @param  array<string, mixed>  $args Arguments to add to request.
+	 * @return string
 	 */
-	public function get( $url = '', $args = array() ) {
-		$query_string = '';
+	public function get( $url, $args = array() ) {
+		if ( ! empty( $args ) ) {
+			$url .= '?' . http_build_query( $args, '', '&' );
+		}
 
 		$curl_handle = curl_init();
-		curl_setopt( $curl_handle, CURLOPT_RETURNTRANSFER, 1 );
+		curl_setopt( $curl_handle, CURLOPT_URL, $url );
+
+		return $this->request( $curl_handle );
+	}
+
+	/**
+	 * @param  \CurlHandle|resource $curl_handle The cURL handler.
+	 * @throws RuntimeException If the request failed or the response is invalid.
+	 * @return string The response body.
+	 */
+	protected function request( $curl_handle ) {
+		curl_setopt( $curl_handle, CURLOPT_RETURNTRANSFER, true );
 		curl_setopt( $curl_handle, CURLOPT_FOLLOWLOCATION, true );
-		if ( ! empty( $args ) ) {
-			$query_string = http_build_query( $args, '', '&' );
-		}
-		curl_setopt( $curl_handle, CURLOPT_URL, $url . '?' . $query_string );
+		curl_setopt( $curl_handle, CURLOPT_FAILONERROR, true );
+
 		$response = curl_exec( $curl_handle );
+
+		$curl_errno = curl_errno( $curl_handle );
+		$curl_error = curl_error( $curl_handle );
 		curl_close( $curl_handle );
 
+		if ( false === $response ) {
+			throw new RuntimeException( sprintf(
+				'cURL error (%d): %s',
+				$curl_errno,
+				$curl_error
+			), $curl_errno );
+		}
+
 		return $response;
 	}
 
diff --git a/src/Plugins/AbstractEddPlugin.php b/src/Plugins/AbstractEddPlugin.php
index cacf139..d575b3c 100644
--- a/src/Plugins/AbstractEddPlugin.php
+++ b/src/Plugins/AbstractEddPlugin.php
@@ -8,6 +8,7 @@
 namespace Junaidbhura\Composer\WPProPlugins\Plugins;
 
 use Composer\Semver\Semver;
+use Exception;
 use UnexpectedValueException;
 
 /**
@@ -15,37 +16,109 @@
  */
 abstract class AbstractEddPlugin extends AbstractPlugin {
 
+	/**
+	 * Get the download URL for this plugin from its API.
+	 *
+	 * @return string
+	 */
+	abstract protected function getDownloadUrlFromApi();
+
 	/**
 	 * Get the download URL for this plugin.
 	 *
-	 * @param  array<string, mixed> $response The EDD API response.
+	 * @throws UnexpectedValueException If the response is invalid.
 	 * @return string
 	 */
-	protected function extractDownloadUrl( array $response ) {
-		if ( empty( $response['download_link'] ) || ! is_string( $response['download_link'] ) ) {
+	public function getDownloadUrl() {
+		try {
+			$response = $this->getDownloadUrlFromApi();
+		} catch ( Exception $e ) {
+			$details = [];
+
+			$error = $e->getMessage();
+			if ( $error ) {
+				$details[] = 'HTTP Error: ' . $error;
+			}
+
+			$message = sprintf(
+				'Could not query API for package %s. Please try again later.',
+				$this->getPackageName()
+			);
+
+			if ( $details ) {
+				$message .= PHP_EOL . PHP_EOL . implode( PHP_EOL . PHP_EOL, $details );
+			}
+
+			throw new UnexpectedValueException( $message );
+		}
+
+		try {
+			/**
+			 * @todo When the Composer plugin drops support for PHP 5,
+			 *    use the `json_decode()` function's `JSON_THROW_ON_ERROR` flag,
+			 *    introduced in PHP 7.3, to simplify error handling.
+			 */
+			$data = json_decode( $response, true );
+
+			if ( json_last_error() !== JSON_ERROR_NONE ) {
+				throw new Exception(
+					json_last_error_msg(),
+					json_last_error()
+				);
+			}
+
+			if ( ! is_array( $data ) ) {
+				throw new UnexpectedValueException(
+					'Expected a data structure'
+				);
+			}
+		} catch ( Exception $e ) {
+			$details = [
+				'json_decode(): ' . $e->getMessage(),
+			];
+
+			$response_length = mb_strlen( $response );
+			if ( $response_length > 0 ) {
+				$details[] = '    ' . mb_substr( $response, 0, 100 ) . ( $response_length > 100 ? '...' : '' );
+			}
+
+			$message = sprintf(
+				'Expected a data structure from API for package %s. Please try again later.',
+				$this->getPackageName()
+			);
+
+			if ( $details ) {
+				$message .= PHP_EOL . PHP_EOL . implode( PHP_EOL . PHP_EOL, $details );
+			}
+
+			throw new UnexpectedValueException( $message );
+		}
+
+		if ( empty( $data['download_link'] ) || ! is_string( $data['download_link'] ) ) {
 			throw new UnexpectedValueException( sprintf(
-				'Expected a valid download URL for package %s',
-				'junaidbhura/' . $this->slug
+				'Expected a valid download URL from API for package %s',
+				$this->getPackageName()
 			) );
 		}
 
-		if ( empty( $response['new_version'] ) || ! is_scalar( $response['new_version'] ) ) {
+		if ( empty( $data['new_version'] ) || ! is_scalar( $data['new_version'] ) ) {
 			throw new UnexpectedValueException( sprintf(
-				'Expected a valid download version number for package %s',
-				'junaidbhura/' . $this->slug
+				'Expected a valid download version number from API for package %s',
+				$this->getPackageName()
 			) );
 		}
 
-		if ( ! Semver::satisfies( $response['new_version'], $this->version ) ) {
+		// If no version is specified, we are fetching the latest version.
+		if ( $this->version && ! Semver::satisfies( $data['new_version'], $this->version ) ) {
 			throw new UnexpectedValueException( sprintf(
-				'Expected download version (%s) to match installed version (%s) of package %s',
-				$response['new_version'],
+				'Expected download version from API (%s) to match installed version (%s) of package %s',
+				$data['new_version'],
 				$this->version,
-				'junaidbhura/' . $this->slug
+				$this->getPackageName()
 			) );
 		}
 
-		return $response['download_link'];
+		return $data['download_link'];
 	}
 
 }
diff --git a/src/Plugins/AbstractPlugin.php b/src/Plugins/AbstractPlugin.php
index 0bab616..b1524a6 100644
--- a/src/Plugins/AbstractPlugin.php
+++ b/src/Plugins/AbstractPlugin.php
@@ -15,14 +15,14 @@ abstract class AbstractPlugin {
 	/**
 	 * The version number of the plugin to download.
 	 *
-	 * @var string Version number.
+	 * @var string
 	 */
 	protected $version = '';
 
 	/**
-	 * The slug of which plugin to download.
+	 * The name of the plugin to download.
 	 *
-	 * @var string Plugin slug.
+	 * @var string
 	 */
 	protected $slug = '';
 
@@ -30,6 +30,7 @@ abstract class AbstractPlugin {
 	 * AbstractPlugin constructor.
 	 *
 	 * @param string $version
+	 * @param string $slug
 	 */
 	public function __construct( $version = '', $slug = '' ) {
 		$this->version = $version;
@@ -43,4 +44,13 @@ public function __construct( $version = '', $slug = '' ) {
 	 */
 	abstract public function getDownloadUrl();
 
+	/**
+	 * Get the plugin's Composer package name with vendor.
+	 *
+	 * @return string
+	 */
+	protected function getPackageName() {
+		return 'junaidbhura/' . $this->slug;
+	}
+
 }
diff --git a/src/Plugins/AcfExtendedPro.php b/src/Plugins/AcfExtendedPro.php
index e5766ff..25f819c 100644
--- a/src/Plugins/AcfExtendedPro.php
+++ b/src/Plugins/AcfExtendedPro.php
@@ -15,21 +15,28 @@
 class AcfExtendedPro extends AbstractEddPlugin {
 
 	/**
-	 * Get the download URL for this plugin.
+	 * Get the download URL for this plugin from its API.
 	 *
 	 * @return string
 	 */
-	public function getDownloadUrl() {
-		$http     = new Http();
-		$response = json_decode( $http->post( 'https://acf-extended.com', array(
+	protected function getDownloadUrlFromApi() {
+		$http = new Http();
+
+		$api_query = array(
 			'edd_action' => 'get_version',
 			'license'    => getenv( 'ACFE_PRO_KEY' ),
 			'item_name'  => 'ACF Extended Pro',
 			'url'        => getenv( 'ACFE_PRO_URL' ),
-			'version'    => $this->version,
-		) ), true );
+		);
+
+		// If no version is specified, we are fetching the latest version.
+		if ( $this->version ) {
+			$api_query['version'] = $this->version;
+		}
+
+		$api_url = 'https://acf-extended.com';
 
-		return $this->extractDownloadUrl( $response );
+		return $http->get( $api_url, $api_query );
 	}
 
 }
diff --git a/src/Plugins/AcfPro.php b/src/Plugins/AcfPro.php
index b84f9bf..4b23bb7 100644
--- a/src/Plugins/AcfPro.php
+++ b/src/Plugins/AcfPro.php
@@ -18,7 +18,20 @@ class AcfPro extends AbstractPlugin {
 	 * @return string
 	 */
 	public function getDownloadUrl() {
-		return 'https://connect.advancedcustomfields.com/index.php?p=pro&a=download&k=' . getenv( 'ACF_PRO_KEY' ) . '&t=' . $this->version;
+		$api_query = array(
+			'p' => 'pro',
+			'a' => 'download',
+			'k' => getenv( 'ACF_PRO_KEY' ),
+		);
+
+		// If no version is specified, we are fetching the latest version.
+		if ( $this->version ) {
+			$api_query['t'] = $this->version;
+		}
+
+		$api_url = 'https://connect.advancedcustomfields.com/index.php';
+
+		return $api_url . '?' . http_build_query( $api_query, '', '&' );
 	}
 
 }
diff --git a/src/Plugins/GravityForms.php b/src/Plugins/GravityForms.php
index 7d3ec56..0a17039 100644
--- a/src/Plugins/GravityForms.php
+++ b/src/Plugins/GravityForms.php
@@ -7,6 +7,7 @@
 
 namespace Junaidbhura\Composer\WPProPlugins\Plugins;
 
+use Exception;
 use Junaidbhura\Composer\WPProPlugins\Http;
 use UnexpectedValueException;
 
@@ -28,20 +29,87 @@ public function __construct( $version = '', $slug = 'gravityforms' ) {
 	/**
 	 * Get the download URL for this plugin.
 	 *
+	 * @throws UnexpectedValueException If the response is invalid.
 	 * @return string
 	 */
 	public function getDownloadUrl() {
-		$http     = new Http();
-		$response = unserialize( $http->post( 'https://gravityapi.com/wp-content/plugins/gravitymanager/api.php?op=get_plugin&slug=' . $this->slug . '&key=' . getenv( 'GRAVITY_FORMS_KEY' ) ) );
+		$http = new Http();
 
-		if ( empty( $response['download_url_latest'] ) || ! is_string( $response['download_url_latest'] ) ) {
+		$api_query = array(
+			'op'   => 'get_plugin',
+			'slug' => $this->slug,
+			'key'  => getenv( 'GRAVITY_FORMS_KEY' ),
+		);
+
+		$api_url = 'https://gravityapi.com/wp-content/plugins/gravitymanager/api.php';
+
+		try {
+			$response = $http->get( $api_url, $api_query );
+		} catch ( Exception $e ) {
+			$details = [];
+
+			$error = $e->getMessage();
+			if ( $error ) {
+				$details[] = 'HTTP Error: ' . $error;
+			}
+
+			$message = sprintf(
+				'Could not query API for package %s. Please try again later.',
+				$this->getPackageName()
+			);
+
+			if ( $details ) {
+				$message .= PHP_EOL . PHP_EOL . implode( PHP_EOL . PHP_EOL, $details );
+			}
+
+			throw new UnexpectedValueException( $message );
+		}
+
+		// Catch any throwables from objects in their unserialization handlers.
+		// Composer itself handles converting PHP notices into exceptions.
+		try {
+			/**
+			 * @todo When the Composer plugin drops support for PHP 5,
+			 *    use the `unserialize()` function's `allowed_classes` option,
+			 *    introduced in PHP 7, to disallow all classes.
+			 */
+			$data = unserialize( $response );
+
+			if ( $data !== false && ! is_array( $data ) ) {
+				throw new UnexpectedValueException(
+					'unserialize(): Expected a data structure'
+				);
+			}
+		} catch ( Exception $e ) {
+			$details = [
+				$e->getMessage(),
+			];
+
+			$response_length = mb_strlen( $response );
+			if ( $response_length > 0 ) {
+				$details[] = '    ' . mb_substr( $response, 0, 100 ) . ( $response_length > 100 ? '...' : '' );
+			}
+
+			$message = sprintf(
+				'Expected a data structure from API for package %s.',
+				$this->getPackageName()
+			);
+
+			if ( $details ) {
+				$message .= PHP_EOL . PHP_EOL . implode( PHP_EOL . PHP_EOL, $details );
+			}
+
+			throw new UnexpectedValueException( $message );
+		}
+
+		if ( empty( $data['download_url_latest'] ) || ! is_string( $data['download_url_latest'] ) ) {
 			throw new UnexpectedValueException( sprintf(
 				'Expected a valid download URL for package %s',
-				'junaidbhura/' . $this->slug
+				$this->getPackageName()
 			) );
 		}
 
-		return str_replace( 'http://', 'https://', $response['download_url_latest'] );
+		return str_replace( 'http://', 'https://', $data['download_url_latest'] );
 	}
 
 }
diff --git a/src/Plugins/NinjaForms.php b/src/Plugins/NinjaForms.php
index 9dca8bc..4b95b74 100644
--- a/src/Plugins/NinjaForms.php
+++ b/src/Plugins/NinjaForms.php
@@ -8,7 +8,7 @@
 namespace Junaidbhura\Composer\WPProPlugins\Plugins;
 
 use Junaidbhura\Composer\WPProPlugins\Http;
-use UnexpectedValueException;
+use InvalidArgumentException;
 
 /**
  * NinjaForms class.
@@ -16,11 +16,12 @@
 class NinjaForms extends AbstractEddPlugin {
 
 	/**
-	 * Get the download URL for this plugin.
+	 * Get the download URL for this plugin from its API.
 	 *
+	 * @throws InvalidArgumentException If the package is unsupported.
 	 * @return string
 	 */
-	public function getDownloadUrl() {
+	protected function getDownloadUrlFromApi() {
 		$name    = '';
 		$env     = null;
 		/**
@@ -296,9 +297,9 @@ public function getDownloadUrl() {
 				break;
 
 			default:
-				throw new UnexpectedValueException( sprintf(
+				throw new InvalidArgumentException( sprintf(
 					'Could not find a matching package for %s. Check the package spelling and that the package is supported',
-					'junaidbhura/' . $this->slug
+					$this->getPackageName()
 				) );
 		}
 
@@ -310,16 +311,23 @@ public function getDownloadUrl() {
 			$url     = ( getenv( "NINJA_FORMS_{$env}_URL" ) ?: $url );
 		}
 
-		$http     = new Http();
-		$response = json_decode( $http->get( 'https://ninjaforms.com', array(
+		$http = new Http();
+
+		$api_query = array(
 			'edd_action' => 'get_version',
 			'license'    => $license,
 			'item_name'  => $name,
 			'url'        => $url,
-			'version'    => $this->version,
-		) ), true );
+		);
+
+		// If no version is specified, we are fetching the latest version.
+		if ( $this->version ) {
+			$api_query['version'] = $this->version;
+		}
+
+		$api_url = 'https://ninjaforms.com';
 
-		return $this->extractDownloadUrl( $response );
+		return $http->get( $api_url, $api_query );
 	}
 
 }
diff --git a/src/Plugins/PolylangPro.php b/src/Plugins/PolylangPro.php
index 66df2cb..f6bff57 100644
--- a/src/Plugins/PolylangPro.php
+++ b/src/Plugins/PolylangPro.php
@@ -15,21 +15,28 @@
 class PolylangPro extends AbstractEddPlugin {
 
 	/**
-	 * Get the download URL for this plugin.
+	 * Get the download URL for this plugin from its API.
 	 *
 	 * @return string
 	 */
-	public function getDownloadUrl() {
-		$http     = new Http();
-		$response = json_decode( $http->post( 'https://polylang.pro', array(
+	protected function getDownloadUrlFromApi() {
+		$http = new Http();
+
+		$api_query = array(
 			'edd_action' => 'get_version',
 			'license'    => getenv( 'POLYLANG_PRO_KEY' ),
 			'item_name'  => 'Polylang Pro',
 			'url'        => getenv( 'POLYLANG_PRO_URL' ),
-			'version'    => $this->version,
-		) ), true );
+		);
+
+		// If no version is specified, we are fetching the latest version.
+		if ( $this->version ) {
+			$api_query['version'] = $this->version;
+		}
+
+		$api_url = 'https://polylang.pro';
 
-		return $this->extractDownloadUrl( $response );
+		return $http->get( $api_url, $api_query );
 	}
 
 }
diff --git a/src/Plugins/PublishPressPro.php b/src/Plugins/PublishPressPro.php
index 81bd86c..2252383 100644
--- a/src/Plugins/PublishPressPro.php
+++ b/src/Plugins/PublishPressPro.php
@@ -8,7 +8,7 @@
 namespace Junaidbhura\Composer\WPProPlugins\Plugins;
 
 use Junaidbhura\Composer\WPProPlugins\Http;
-use UnexpectedValueException;
+use InvalidArgumentException;
 
 /**
  * PublishPressPro class.
@@ -26,11 +26,12 @@ public function __construct( $version = '', $slug = 'publishpress-planner-pro' )
 	}
 
 	/**
-	 * Get the download URL for this plugin.
+	 * Get the download URL for this plugin from its API.
 	 *
+	 * @throws InvalidArgumentException If the package is unsupported.
 	 * @return string
 	 */
-	public function getDownloadUrl() {
+	protected function getDownloadUrlFromApi() {
 		$id  = 0;
 		$env = null;
 		/**
@@ -89,9 +90,9 @@ public function getDownloadUrl() {
 				break;
 
 			default:
-				throw new UnexpectedValueException( sprintf(
+				throw new InvalidArgumentException( sprintf(
 					'Could not find a matching package for %s. Check the package spelling and that the package is supported',
-					'junaidbhura/' . $this->slug
+					$this->getPackageName()
 				) );
 		}
 
@@ -103,16 +104,23 @@ public function getDownloadUrl() {
 			$url     = ( getenv( "PUBLISHPRESS_{$env}_PRO_URL" ) ?: $url );
 		}
 
-		$http     = new Http();
-		$response = json_decode( $http->get( 'https://publishpress.com', array(
+		$http = new Http();
+
+		$api_query = array(
 			'edd_action' => 'get_version',
 			'license'    => $license,
 			'item_id'    => $id,
 			'url'        => $url,
-			'version'    => $this->version,
-		) ), true );
+		);
+
+		// If no version is specified, we are fetching the latest version.
+		if ( $this->version ) {
+			$api_query['version'] = $this->version;
+		}
+
+		$api_url = 'https://publishpress.com';
 
-		return $this->extractDownloadUrl( $response );
+		return $http->get( $api_url, $api_query );
 	}
 
 }
diff --git a/src/Plugins/WpAiPro.php b/src/Plugins/WpAiPro.php
index 6041f56..6ddbcde 100644
--- a/src/Plugins/WpAiPro.php
+++ b/src/Plugins/WpAiPro.php
@@ -25,11 +25,11 @@ public function __construct( $version = '', $slug = 'wp-all-import-pro' ) {
 	}
 
 	/**
-	 * Get the download URL for this plugin.
+	 * Get the download URL for this plugin from its API.
 	 *
 	 * @return string
 	 */
-	public function getDownloadUrl() {
+	protected function getDownloadUrlFromApi() {
 		$url     = '';
 		$name    = '';
 		$license = '';
@@ -75,16 +75,23 @@ public function getDownloadUrl() {
 			}
 		}
 
-		$http     = new Http();
-		$response = json_decode( $http->get( 'https://www.wpallimport.com', array(
+		$http = new Http();
+
+		$api_query = array(
 			'edd_action' => 'get_version',
 			'license'    => $license,
 			'item_name'  => $name,
 			'url'        => $url,
-			'version'    => $this->version,
-		) ), true );
+		);
+
+		// If no version is specified, we are fetching the latest version.
+		if ( $this->version ) {
+			$api_query['version'] = $this->version;
+		}
+
+		$api_url = 'https://www.wpallimport.com';
 
-		return $this->extractDownloadUrl( $response );
+		return $http->get( $api_url, $api_query );
 	}
 
 }
diff --git a/src/Plugins/Wpml.php b/src/Plugins/Wpml.php
index b1ad222..984f7d9 100644
--- a/src/Plugins/Wpml.php
+++ b/src/Plugins/Wpml.php
@@ -7,7 +7,7 @@
 
 namespace Junaidbhura\Composer\WPProPlugins\Plugins;
 
-use UnexpectedValueException;
+use InvalidArgumentException;
 
 /**
  * Wpml class.
@@ -27,6 +27,7 @@ public function __construct( $version = '', $slug = 'wpml-sitepress-multilingual
 	/**
 	 * Get the download URL for this plugin.
 	 *
+	 * @throws InvalidArgumentException If the package is unsupported.
 	 * @return string
 	 */
 	public function getDownloadUrl() {
@@ -51,13 +52,26 @@ public function getDownloadUrl() {
 		);
 
 		if ( ! array_key_exists( $this->slug, $packages ) ) {
-			throw new UnexpectedValueException( sprintf(
+			throw new InvalidArgumentException( sprintf(
 				'Could not find a matching package for %s. Check the package spelling and that the package is supported',
-				'junaidbhura/' . $this->slug
+				$this->getPackageName()
 			) );
 		}
 
-		return 'https://wpml.org/?download=' . $packages[ $this->slug ] . '&user_id=' . getenv( 'WPML_USER_ID' ) . '&subscription_key=' . getenv( 'WPML_KEY' ) . '&version=' . $this->version;
+		$api_query = array(
+			'download'         => $packages[ $this->slug ],
+			'user_id'          => getenv( 'WPML_USER_ID' ),
+			'subscription_key' => getenv( 'WPML_KEY' ),
+		);
+
+		// If no version is specified, we are fetching the latest version.
+		if ( $this->version ) {
+			$api_query['version'] = $this->version;
+		}
+
+		$api_url = 'https://wpml.org/';
+
+		return $api_url . '?' . http_build_query( $api_query, '', '&' );
 	}
 
 }