Crass: Incorrect tokenization of bad URLs enables CSS sanitizer bypass

[ Description ]Official description

Crass is a Ruby CSS parser that is compliant with the CSS Syntax Level 3 specification. Prior to 1.0.8, Crass incorrectly treats a closing parenthesis after an escaped backslash as escaped while consuming the remnants of a bad URL. Crass therefore keeps declarations, style rules, or at-rules inside a bad URL token even though a browser treats them as live CSS. A sanitizer that parses untrusted CSS with Crass and reserializes it without rejecting the bad URL can allow CSS used for UI redress, external resource loading, or CSS-based data exfiltration, but this issue does not enable script execution in modern browsers. This issue is fixed in version 1.0.8.

[ Fixes ]Fixes and patches

• crass 1.0.8Fixed version · GitHub Advisories · rubygems package crass: upgrade to 1.0.8 or later (affected <= 1.0.7)

[ Packages ]Affected open-source packages

• crass rubygemsAffected <= 1.0.7 · fixed in 1.0.8 · GHSA-pq4g-8rxf-4g29

[ References ]References

• github.com/rgrove/crass/commit/689fc45c632fdf3803b2f4e844ffc9cca3b08f34
• github.com/rgrove/crass/releases/tag/v1.0.8
• github.com/rgrove/crass/security/advisories/GHSA-pq4g-8rxf-4g29