Impact
Using carefully crafted input, an attacker may be able to sneak arbitrary HTML and CSS through Sanitize >= 3.0.0, < 6.0.2 when Sanitize is configured to use the built-in "relaxed" config or when using a custom config that allows style elements and one or more CSS at-rules. This could result in XSS (cross-site scripting) or other undesired behavior when the malicious HTML and CSS are rendered in a browser.
Patches
Sanitize >= 6.0.2 performs additional escaping of CSS in style element content, which fixes this issue.
Workarounds
Users who are unable to upgrade can prevent this issue by using a Sanitize config that doesn't allow style elements, using a Sanitize config that doesn't allow CSS at-rules, or by manually escaping the character sequence </ as <\/ in style element content.
Credit
This issue was found by @cure53 during an audit of a project that uses Sanitize and was reported by one of that project's maintainers. Thank you!
References
cure53 Finder
Impact
Using carefully crafted input, an attacker may be able to sneak arbitrary HTML and CSS through Sanitize
>= 3.0.0, < 6.0.2when Sanitize is configured to use the built-in "relaxed" config or when using a custom config that allowsstyleelements and one or more CSS at-rules. This could result in XSS (cross-site scripting) or other undesired behavior when the malicious HTML and CSS are rendered in a browser.Patches
Sanitize
>= 6.0.2performs additional escaping of CSS instyleelement content, which fixes this issue.Workarounds
Users who are unable to upgrade can prevent this issue by using a Sanitize config that doesn't allow
styleelements, using a Sanitize config that doesn't allow CSS at-rules, or by manually escaping the character sequence</as<\/instyleelement content.Credit
This issue was found by @cure53 during an audit of a project that uses Sanitize and was reported by one of that project's maintainers. Thank you!
References