CVE-2026-63466: Unleash

Medium severity, CVSS 4.1. EPSS: 0.3% chance of exploitation in the next 30 days.

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 products

• Unleash Unleash: before 8.0.3 (fixed in 8.0.3)

Published 2026-08-21. Last modified 2026-09-09.