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CVE-2026-63466
Published:August 21, 2026
Updated:September 24, 2026
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.
Affected Packages
https://github.com/Unleash/unleash.git (GITHUB):
Affected version(s) >=v5.0.0 <v8.0.3
Fix Suggestion:
Update to version v8.0.3
unleash-server (NPM):
Affected version(s) >=1.0.0-alpha.1 <8.0.3
Fix Suggestion:
Update to version 8.0.3
unleash-server (NPM):
Affected version(s) >=1.0.0-alpha.1 <8.0.3
Fix Suggestion:
Update to version 8.0.3
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CVSS v4
Base Score:
5.1
Attack Vector
NETWORK
Attack Complexity
LOW
Attack Requirements
NONE
Privileges Required
LOW
User Interaction
PASSIVE
Vulnerable System Confidentiality
NONE
Vulnerable System Integrity
LOW
Vulnerable System Availability
NONE
Subsequent System Confidentiality
NONE
Subsequent System Integrity
LOW
Subsequent System Availability
NONE
CVSS v3
Base Score:
4.1
Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
LOW
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
NONE
Integrity
LOW
Availability
NONE
Weakness Type (CWE)
Improper Encoding or Escaping of Output
EPSS
Base Score:
0.18