How severe is CVE-2025-25299?

No CVSS score has been assigned to CVE-2025-25299 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2025-25299?

CVE-2025-25299 affects the following packages: @ckeditor/ckeditor5-real-time-collaboration (npm), ckeditor5-premium-features (npm). Ecosystems affected: npm.

How do I fix CVE-2025-25299?

Update @ckeditor/ckeditor5-real-time-collaboration to 44.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-25299 is resolved across your whole dependency graph.

How do I detect CVE-2025-25299 in my npm dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @ckeditor/ckeditor5-real-time-collaboration, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2025-25299 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-2025-25299 actively exploited in the wild?

No public exploit code has been indexed for CVE-2025-25299 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-2025-25299?

CVE-2025-25299 has an EPSS (Exploit Prediction Scoring System) score of 0.6%, placing it in the 49th 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-2025-25299?

CVE-2025-25299 is classified as Cross-site Scripting (XSS) (CWE-79), CWE-80 (CWE-80). These weakness types 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-2025-25299 published, and has it been updated?

CVE-2025-25299 was published on February 20, 2025 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CVE-2025-25299: @ckeditor/ckeditor5-real

EPSS Exploitation Probability

via FIRST.org ↗

0.6%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs49th percentile — riskier than 49% of all scored CVEsHighest risk

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

Real-World Exposure

2 pkgs 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.

11other npm packages depend on this — each one inherits the vulnerability until it's patched upstream

@ckeditor/ckeditor5-real-time-collaborationnpm

174Kdownloads / week

ckeditor5-premium-featuresnpm

118Kdownloads / week

Description

CKEditor 5 is a modern JavaScript rich-text editor with an MVC architecture. During a recent internal audit, a Cross-Site Scripting (XSS) vulnerability was discovered in the CKEditor 5 real-time collaboration package. This vulnerability affects user markers, which represent users' positions within the document. It can lead to unauthorized JavaScript code execution, which might happen with a very specific editor and token endpoint configuration. This vulnerability affects only installations with Real-time collaborative editing enabled. The problem has been recognized and patched. The fix is available in version 44.2.1 (and above). Users are advised to upgrade. There are no known workarounds for this vulnerability.

Affected Packages

2 total 2 fixed

Ecosystem	Package	Vulnerable range	Fix
📦npm	`@ckeditor/ckeditor5-real-time-collaboration`	≥ 41.3.0&&< 44.2.1	44.2.1`npm install @ckeditor/ckeditor5-real-time-collaboration@44.2.1`
📦npm	`ckeditor5-premium-features`	≥ 42.0.0&&< 44.2.1	44.2.1`npm install ckeditor5-premium-features@44.2.1`

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for @ckeditor/ckeditor5-real-time-collaboration, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update @ckeditor/ckeditor5-real-time-collaboration to 44.2.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-25299 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

CKEditor 5 is a modern JavaScript rich-text editor with an MVC architecture. During a recent internal audit, a Cross-Site Scripting (XSS) vulnerability was discovered in the CKEditor 5 real-time collaboration package. This vulnerability affects user markers, which represent users' positions within the document. It can lead to unauthorized JavaScript code execution, which might happen with a very specific editor and token endpoint configuration. This vulnerability affects only installations with Real-time collaborative editing enabled. The problem has been recognized and patched. The fix is ava

O3 Security · Impact-Aware SCA

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CVE-2025-25299 — @ckeditor/ckeditor5-real-…