Mattermost versions 9.5.x <= 9.5.3, 9.6.x <= 9.6.1 and 8.1.x <= 8.1.12 fail to perform proper input validation on post actions which allows an attacker to run a playbook checklist task command as another user via creating and sharing a deceptive post action that unexpectedly runs a slash command in some arbitrary channel.
| Software | From | Fixed in |
|---|---|---|
| mattermost / mattermost_server | 8.1.0 | 8.1.13 |
| mattermost / mattermost_server | 9.5.0 | 9.5.4 |
| mattermost / mattermost_server | 9.6.0 | 9.6.2 |