Description
An issue was discovered in PostCSS before 8.4.31. The vulnerability affects linters using PostCSS to parse external untrusted CSS. An attacker can prepare CSS in such a way that it will contains parts parsed by PostCSS as a CSS comment. After processing by PostCSS, it will be included in the PostCSS output in CSS nodes (rules, properties) despite being included in a comment.
Remediation
References
https://github.com/postcss/postcss/blob/main/lib/tokenize.js#L25
https://github.com/postcss/postcss/commit/58cc860b4c1707510c9cd1bc1fa30b423a9ad6c5
https://github.com/postcss/postcss/releases/tag/8.4.31
https://github.com/github/advisory-database/issues/2820