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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.

How do I mitigate CVE-2026-55090 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-55090?

O3 pinpoints whether CVE-2026-55090 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

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.

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

CVE-2026-55090 was published on August 17, 2026 and was last updated on August 17, 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

Fix: ether/etherpad#7905

CVE-2026-55090 is a security vulnerability in ep_etherpad-lite. O3 Security confirms whether CVE-2026-55090 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.

Etherpad has stored XSS in HTML export via unescaped attribute-pool values

Published

Aug 17, 2026

Updated

Aug 17, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Aug 17, 2026 · OSV.dev, 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

253downloads / 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

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. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-55090 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.

Tailored to CVE-2026-55090. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

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?

O3 detects CVE-2026-55090 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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