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CVE-2026-50290: SpecifyJS: Legacy Browsers at Risk of CSS Injection

CVE-2026-50290 · published 2 months ago

Summary

SpecifyJS, a CSS processor, has a security flaw in its older version. This flaw allows attackers to inject malicious code into web pages, but only affects older Internet Explorer browsers (IE6-IE10). The issue has been fixed in a newer version of SpecifyJS, so users should update to the latest version to stay secure.

What to do

Update asymmetric-effort specifyjs to version 0.2.136.

Affected software

Ecosystem	Vendor	Product	Affected versions
npm	asymmetric-effort	specifyjs	< 0.2.136 Fix: upgrade to 0.2.136
–	asymmetric-effort	specifyjs	< 0.2.136

Original advisory text

@asymmetric-effort/specifyjs: CSS expression sanitization is bypassable in renderToString

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.

References

https://github.com/advisories/GHSA-93q6-wwjh-jc6h
https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/50xxx/CVE-2026-50290... Vendor Advisory
https://nvd.nist.gov/vuln/detail/CVE-2026-50290 Vendor Advisory
https://github.com/asymmetric-effort/specifyjs/commit/25d1fb491d99479efdf501f5f7... Patch
https://github.com/asymmetric-effort/specifyjs/security/advisories/GHSA-93q6-wwj... Vendor Advisory

Fix within

Internet-facing 60 days

Internal At next upgrade

Not known to be exploited
Needs hands-on effort to exploit
Gives an attacker partial control

Severity

7.5 High

Exploitation

<1% chance of attack within 30 days

Type

CWE-79Cross-site Scripting (XSS)

Timeline

Published21 Aug 2026

Updated4 Nov 2026

First seen2 Jul 2026

Sources

GHSA-93q6-wwjh-jc6h · GHSA

CVE-2026-50290 · NVD

CVE-2026-50290 · MITRE

CVE-2026-50290 · OSV

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