Poor performance of a particular example on ie 6

[marekdedic]

Hi I get very poor performance for elements with :focus:hover when checking them against ie 6.
Example:

$ time doiuse --browsers "ie 6" example.css
example.css:1:1: CSS 2.1 selectors not supported by: IE (6) (css-sel2)
doiuse --browsers "ie 6" example.css  59,04s user 0,06s system 100% cpu 59,014 total

where example.css is:

.imagelightbox-arrow:focus:hover {
}

I've found that changing the name of the class sometimes resolves the issue, as does removing either the hover or the focus. From what I can tell, the content of the class has no effect.

I am using version 4.2.0

[marekdedic]

I tried profiling the problem and 99% of the time is spent in
RegExp: ^((\[[^\]]*\]|\([^\)]*\))?[^\[\]\(\)]*)*\.

[marekdedic]

processed.txt

[marekdedic]

See here - catastrophic backtracking:
https://regex101.com/r/MlbAhW/1