CVE-2021-25987 is a medium-severity (CVSS 4.6) Cross-site Scripting (XSS) vulnerability in hexo. A fix is available for hexo — see the affected versions and patch details below.
Hexo Vulnerable to XSS
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2021-25987.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-25987 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,386 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.
hexonpmDescription
Hexo versions 0.0.1 to 5.4.0 are vulnerable against stored XSS. The post “body” and “tags” don’t sanitize malicious javascript during web page generation. Local unprivileged attacker can inject arbitrary code.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | hexo | ≥ 0.0.1&&< 6.0.0 | 6.0.0npm install hexo@6.0.0 |
Affected Products
hexohexoDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for hexo, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update hexo to 6.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-25987 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-2021-25987 in your dependencies?
Find it across npm, including transitive dependencies.