Mattermost versions 11.3.x <= 11.3.0 fail to preserve the redacted state of burn-on-read posts during deletion which allows channel members to access unrevealed burn-on-read message contents via the WebSocket post deletion event.. Mattermost Advisory ID: MMSA-2026-00579
Weakness
The code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor.
Potential Mitigations
- Compartmentalize the system to have “safe” areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
- Ensure that appropriate compartmentalization is built into the system design, and the compartmentalization allows for and reinforces privilege separation functionality. Architects and designers should rely on the principle of least privilege to decide the appropriate time to use privileges and the time to drop privileges.
Related Attack Patterns
- https://cwe.mitre.org/data/definitions/12.html
- https://cwe.mitre.org/data/definitions/217.html
- https://cwe.mitre.org/data/definitions/612.html
- https://cwe.mitre.org/data/definitions/613.html
- https://cwe.mitre.org/data/definitions/618.html
- https://cwe.mitre.org/data/definitions/619.html
- https://cwe.mitre.org/data/definitions/621.html
- https://cwe.mitre.org/data/definitions/622.html
- https://cwe.mitre.org/data/definitions/623.html