PrimeFaces Extensions only supports the latest major version. We are a small community and are resource constrained to maintain multiple versions. However if it is a severe vulnerability we may backport it upon request.
Please report the issue on the Issues page: https://github.com/primefaces-extensions/primefaces-extensions/issues
After review it will be marked with a "security" label if found to be valid and addressed quickly if possible!