Vulnerability Description
Unleash is an open-source feature management platform. Prior to 8.0.3, FeatureEventFormatterMd.format in src/lib/addons/feature-event-formatter-md.ts assigns Mustache.escape to an identity function before rendering action and path templates. Because Mustache.escape is process-wide, the assignment disables escaping for subsequent Mustache.render calls in email-service.ts, webhook.ts, datadog.ts, and new-relic.ts. An editor-level user can place Slack or Microsoft Teams link syntax in an unrestricted username, trigger a feature event, and inject an attacker-labeled link into a trusted outbound notification channel, while other Mustache sinks remain unescaped until restart. This issue is fixed in version 8.0.3.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/Unleash/unleash/commit/002012cfdbedd2e9b7db9dc83b9f549f761db2
- https://github.com/Unleash/unleash/releases/tag/v8.0.3
- https://github.com/Unleash/unleash/security/advisories/GHSA-w4mq-xh27-6xpx
FAQ
What is CVE-2026-63466?
CVE-2026-63466 is a vulnerability with a CVSS score of 4.1 (MEDIUM). Unleash is an open-source feature management platform. Prior to 8.0.3, FeatureEventFormatterMd.format in src/lib/addons/feature-event-formatter-md.ts assigns Mustache.escape to an identity function be...
How severe is CVE-2026-63466?
CVE-2026-63466 has been rated MEDIUM with a CVSS base score of 4.1/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-63466?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.