How severe is CVE-2026-50290?

No CVSS score has been assigned to CVE-2026-50290 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-50290?

CVE-2026-50290 affects the following packages: @asymmetric-effort/specifyjs (npm). Ecosystems affected: npm.

How do I fix CVE-2026-50290?

Update @asymmetric-effort/specifyjs to 0.2.136 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-50290 is resolved across your whole dependency graph.

How do I detect CVE-2026-50290 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @asymmetric-effort/specifyjs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-50290 if there is no patch (or I can't update yet)?

Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Is CVE-2026-50290 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-50290 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-50290?

CVE-2026-50290 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 41th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-50290?

CVE-2026-50290 is classified as Cross-site Scripting (XSS) (CWE-79). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-50290 published, and has it been updated?

CVE-2026-50290 was published on August 21, 2026 and was last updated on October 21, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

📦 npm

Not in CISA KEV

CVE-2026-50290 — @asymmetric-effort/specif…

Fix: asymmetric-effort/specifyjs@25d1fb4

CVE-2026-50290 is a Cross-site Scripting (XSS) vulnerability in @asymmetric-effort/specifyjs. A fix is available for @asymmetric-effort/specifyjs — see the affected versions and patch details below.

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

Also known asGHSA-93q6-wwjh-jc6h

Published

Aug 21, 2026

Updated

Oct 21, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 20, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-50290.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs41th percentile — riskier than 41% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.

0other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@asymmetric-effort/specifyjsnpm

419downloads / week

Description

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

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@asymmetric-effort/specifyjs`	all versions	0.2.136`npm install @asymmetric-effort/specifyjs@0.2.136`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @asymmetric-effort/specifyjs, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @asymmetric-effort/specifyjs to 0.2.136 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-50290 is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

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.

O3 Security · Impact-Aware SCA

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