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.
Mattermost versions 9.5.x <= 9.5.3, 9.7.x <= 9.7.1, 9.6.x <= 9.6.1 and 8.1.x <= 8.1.12 fail to check if the email signup configuration option is enabled when a user requests to switch from SAML to Email. This allows the user to switch their authentication mail from SAML to email and possibly edit personal details that were otherwise non-editable and provided by the SAML provider.
Mattermost versions 9.5.x <= 9.5.3, 9.6.x <= 9.6.1, 8.1.x <= 8.1.12 fail to restrict the audience of the "custom_playbooks_playbook_run_updated" webhook event, which allows a guest on a channel with a playbook run linked to see all the details of the playbook run when the run is marked by finished.
Mattermost versions 9.5.x <= 9.5.3, 9.6.x <= 9.6.1, 8.1.x <= 8.1.12 fail to enforce proper access controls for channel and team membership when linking a playbook run to a channel which allows members to link their runs to private channels they were not members of.
Mattermost versions 9.5.x <= 9.5.3, 9.7.x <= 9.7.1 and 8.1.x <= 8.1.12 fail to perform a proper authorization check in the /api/v4/groups/<group-id>/channels/<channel-id>/link endpoint which allows a user to learn the members of an AD/LDAP group that is linked to a team by adding the group to a channel, even if the user has no access to the team.
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 access control which allows a guest to get the metadata of a public playbook run that linked to the channel they are guest via sending an RHSRuns GraphQL query request to the server
Mattermost versions 9.5.x <= 9.5.3, 9.6.x <= 9.6.1 and 8.1.x <= 8.1.12 fail to enforce proper access controls which allows user to view arbitrary post contents via the /playbook add slash command
Mattermost versions 9.5.x <= 9.5.3, 9.7.x <= 9.7.1, 9.6.x <= 9.6.1, 8.1.x <= 8.1.12 fail to enforce proper access control which allows a user to run a slash command in a channel they are not a member of via linking a playbook run to that channel and running a slash command as a playbook task command.
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 authorization checks which allows a member running a playbook in an existing channel to be promoted to a channel admin
Mattermost versions 9.6.0, 9.5.x before 9.5.3, and 8.1.x before 8.1.12 fail to fully validate role changes which allows an attacker authenticated as team admin to demote users to guest via crafted HTTP requests.