Unleash up to 8.0.2 Feature Event Formatter feature-event-formatter-md.ts FeatureEventFormatterMd.format cross site scripting

Summaryinfo

A vulnerability, which was classified as problematic, was found in Unleash up to 8.0.2. This impacts the function FeatureEventFormatterMd.format of the file src/lib/addons/feature-event-formatter-md.ts of the component Feature Event Formatter. Such manipulation leads to cross site scripting. This vulnerability is uniquely identified as CVE-2026-63466. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability was found in Unleash up to 8.0.2. It has been rated as problematic. Affected by this issue is the function FeatureEventFormatterMd.format of the file src/lib/addons/feature-event-formatter-md.ts of the component Feature Event Formatter. The manipulation with an unknown input leads to a cross site scripting vulnerability. Using CWE to declare the problem leads to CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Impacted is integrity. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-63466 since 07/16/2026. The exploitation is known to be easy. The attack may be launched remotely. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1059.007.

Upgrading to version 8.0.3 eliminates this vulnerability.

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Productinfo

Name

• Unleash

Version

• 8.0.0
• 8.0.1
• 8.0.2

Website

• Product: https://github.com/Unleash/unleash/

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