CVE-2026-50290: Asymmetric-Effort Specifyjs

Medium severity, CVSS 5.3. EPSS: 0.5% chance of exploitation in the next 30 days.

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 products

• Asymmetric-Effort Specifyjs: before 0.2.136 (fixed in 0.2.136)

Published 2026-08-21. Last modified 2026-09-30.