AIKIDO-2026-634061
html_sanitize_ex is vulnerable to CSS Injection
23
CVE Score
Low
CSS Injection
TL;DR
The CSS scrubber applies its property and value allowlist only to substrings that match a property: value declaration pattern, so input that does not match that pattern is copied to the output unchanged. This lets CSS at-rules such as @import url(...) survive sanitizing and pull in a remote stylesheet or inject styling into a page shown to other users. The fix inspects and neutralizes at-rules instead of passing unmatched input through.
How do I fix this?
Upgrade the html_sanitize_ex library to the patch version.
Who does this affect?
You are affected if you are using a version that falls within the vulnerable range and you use the HtmlSanitizeEx.html5/1 scrubber, or call HtmlSanitizeEx.Scrubber.CSS.scrub/1 directly, on style element content that is rendered to other users.
Package
Versions
0.3.1 - 1.5.3
Fixed in 1.5.4Background info
html_sanitize_ex is vulnerable to CSS Injection in versions 0.3.1 - 1.5.3.
Links
GitHub Release
Fix Commits
github.com/rrrene/html_sanitize_ex/commit/0b9f9ad63a7529d4f2c3c1134c371adc3e654308github.com/rrrene/html_sanitize_ex/commit/c311a499db0b0baef06493fb3cfeb730c0f18f28
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