medium5.3
CVE-2026-50290
@asymmetric-effort/specifyjs: CSS expression sanitization is bypassable in renderToString
Impact
SpecifyJS is a declarative TypeScript user interface framework. Prior to version 0.2.136, CSS value sanitization stripped `expression(` and `url(javascript:` using simple regex, but could be bypassed with CSS unicode escapes (`\65xpression(`), null bytes, or CSS comments (`exp/**/ression(`). These CSS injection vectors only work in legacy browsers (IE6-IE10). SpecifyJS targets modern browsers. Starting in version 0.2.136, CSS sanitization now normalizes unicode escapes and strips CSS comments before pattern matching. Also checks for `behavior:`, `-moz-binding`, and `-o-link` patterns.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | @asymmetric-effort/specifyjs | < 0.2.136 | 0.2.136 |