CVE-2026-40300: Zulip: Message edit history visible in "moves only" policy through /api/v1/messages/{id}/history

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-05-12 · updated 2026-06-17
Weakness: CWE-284

Description

Zulip is an open-source team collaboration tool. Prior to 12.0, With message_edit_history_visibility_policy set to "moves", /api/v1/messages/{id}/history still returns historical content values, allowing low-privilege users to recover text that was edited away from other users' messages. This vulnerability is fixed in 12.0.

Affected products

zulip: 10.0

References

https://github.com/zulip/zulip/security/advisories/GHSA-jp8f-mvv6-89cr
https://github.com/zulip/zulip/security/advisories/GHSA-jp8f-mvv6-89cr

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