How severe is CVE-2026-55090?

No CVSS score has been assigned to CVE-2026-55090 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-55090?

CVE-2026-55090 affects the following packages: ep_etherpad-lite (npm). Ecosystems affected: npm.

How do I fix CVE-2026-55090?

Update ep_etherpad-lite to 3.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55090 is resolved across your whole dependency graph.

How do I detect CVE-2026-55090 in my npm dependencies?

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

How do I mitigate CVE-2026-55090 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-2026-55090 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-55090 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-2026-55090?

CVE-2026-55090 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 44th 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-2026-55090?

CVE-2026-55090 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-2026-55090 published, and has it been updated?

CVE-2026-55090 was published on August 19, 2026 and was last updated on September 11, 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-2026-55090 — ep_etherpad-lite

Fix: ether/etherpad@86c56cf

CVE-2026-55090 is a Cross-site Scripting (XSS) vulnerability in ep_etherpad-lite. A fix is available for ep_etherpad-lite — see the affected versions and patch details below.

Etherpad: Stored XSS in HTML export via unescaped attribute-pool values

Also known asGHSA-2jp7-wwpg-3p9w

Published

Aug 19, 2026

Updated

Sep 11, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 2, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
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-2026-55090.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs44th percentile — riskier than 44% 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.

2other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

ep_etherpad-litenpm

418downloads / week

Description

Fix: PR #7905 (ether/etherpad).

getHTMLFromAtext in src/node/utils/ExportHtml.ts interpolates values from the exportHtmlAdditionalTagsWithData plugin hook into span data-<k>="<v>" without HTML-attribute escaping. The value comes verbatim from the pad attribute pool, which a pad editor controls via a crafted changeset (only author attributes are validated; moveOpsToNewPool -> AttributePool.putAttrib stores any value). With a bundled plugin that registers the hook (ep_font_color / ep_font_size), an attribute value such as " onload="alert(1) is exported as <span data-color="" onload="alert(1)"> and served as text/html, yielding stored XSS for any collaborator who opens the export.

Fix: escape the name and value via Security.escapeHTMLAttribute. PR #7905 also adds a startup warning when default/placeholder account or SSO credentials are configured (defense-in-depth, non-breaking).

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`ep_etherpad-lite`	all versions	3.3.0`npm install ep_etherpad-lite@3.3.0`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ep_etherpad-lite, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update ep_etherpad-lite to 3.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-55090 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

Fix: PR #7905 (ether/etherpad). `getHTMLFromAtext` in `src/node/utils/ExportHtml.ts` interpolates values from the `exportHtmlAdditionalTagsWithData` plugin hook into `span data-<k>="<v>"` without HTML-attribute escaping. The value comes verbatim from the pad attribute pool, which a pad editor controls via a crafted changeset (only `author` attributes are validated; `moveOpsToNewPool` -> `AttributePool.putAttrib` stores any value). With a bundled plugin that registers the hook (ep_font_color / ep_font_size), an attribute value such as `" onload="alert(1)` is exported as `<span data-color="" on

O3 Security · Impact-Aware SCA

Is CVE-2026-55090 in your dependencies?

Find it across npm, including transitive dependencies.

Scan my dependencies How O3 SCA works