CVE-2021-25978 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in apostrophe. A fix is available for apostrophe — see the affected versions and patch details below.
Cross-site Scripting in apostrophe
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-2021-25978.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-25978 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
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.
apostrophenpmDescription
Apostrophe CMS versions between 2.63.0 to 3.3.1 are vulnerable to Stored XSS where an editor uploads an SVG file that contains malicious JavaScript onto the Images module, which triggers XSS once viewed.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | apostrophe | ≥ 2.63.0&&< 3.4.0 | 3.4.0npm install apostrophe@3.4.0 |
Affected Products
apostrophecmsapostrophecmsDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for apostrophe, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update apostrophe to 3.4.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-25978 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
Is CVE-2021-25978 in your dependencies?
Find it across npm, including transitive dependencies.