Summary
@asymmetric-effort/specifyjs: CSS expression sanitization is bypassable in renderToString
Finding
Location: core/src/server/render-to-string.ts:307-311
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().
Mitigating Factor: These CSS injection vectors only work in legacy browsers (IE6-IE10). SpecifyJS targets modern browsers.
Status
Fixed in v0.2.136, CSS sanitization now normalizes unicode escapes and strips CSS comments before pattern matching. Also checks for behavior:, -moz-binding, and -o-link patterns.
Impact
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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Frequently Asked Questions
- What is CVE-2026-50290? CVE-2026-50290 is a medium-severity cross-site scripting (XSS) vulnerability in @asymmetric-effort/specifyjs (npm), affecting versions < 0.2.136. It is fixed in 0.2.136. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which versions of @asymmetric-effort/specifyjs are affected by CVE-2026-50290? @asymmetric-effort/specifyjs (npm) versions < 0.2.136 is affected.
- Is there a fix for CVE-2026-50290? Yes. CVE-2026-50290 is fixed in 0.2.136. Upgrade to this version or later.
- Is CVE-2026-50290 exploitable, and should I be worried? Whether CVE-2026-50290 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-50290 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-50290? Upgrade
@asymmetric-effort/specifyjsto 0.2.136 or later.