Mattermost version 2.10.0 and earlier fails to sanitize deeplink paths, which allows an attacker to perform CSRF attacks against the server.

Mattermost fails to perform proper authorization in the /plugins/focalboard/api/v2/users endpoint allowing an attacker who is a guest user and knows the ID of another user to get their information (e.g. name, surname, nickname) via Mattermost Boards.

Mattermost fails to limit the log size of server logs allowing an attacker sending specially crafted requests to different endpoints to potentially overflow the log.

Mattermost fails to limit the amount of data extracted from compressed archives during board import in Mattermost Boards allowing an attacker to consume excessive resources, possibly leading to Denial of Service, by importing a board using a specially crafted zip (zip bomb).

Mattermost fails to properly check a redirect URL parameter allowing for an open redirect was possible when the user clicked "Back to Mattermost" after providing a invalid custom url scheme in /oauth/{service}/mobile_login?redirect_to=

Mattermost fails to properly validate the "Show Full Name" option in a few endpoints in Mattermost Boards, allowing a member to get the full name of another user even if the Show Full Name option was disabled. 

Mattermost fails to check whether the  “Allow users to view archived channels”  setting is enabled during permalink previews display, allowing members to view permalink previews of archived channels even if the “Allow users to view archived channels” setting is disabled. 

Mattermost fails to properly limit the characters allowed in different fields of a block in Mattermost Boards allowing a attacker to consume excessive resources, possibly leading to Denial of Service, by patching the field of a block using a specially crafted string. 

Mattermost fails to use  innerText / textContent when setting the channel name in the webapp during autocomplete, allowing an attacker to inject HTML to a victim's page by create a channel name that is valid HTML. No XSS is possible though. 

Mattermost fails to check if hardened mode is enabled when overriding the username and/or the icon when posting a post. If settings allowed integrations to override the username and profile picture when posting, a member could also override the username and icon when making a post even if the Hardened Mode setting was enabled

Mattermost fails to properly sanitize the request to /api/v4/redirect_location allowing an attacker, sending a specially crafted request to /api/v4/redirect_location, to fill up the memory due to caching large items.

Mattermost fails to properly sanitize the user object when updating the username, resulting in the password hash being included in the response body. 

Mattermost fails to properly validate requests to the Calls plugin, allowing an attacker sending a request without a User Agent header to cause a panic and crash the Calls plugin

Mattermost Mobile fails to limit the maximum number of Markdown elements in a post allowing an attacker to send a post with hundreds of emojis to a channel and freeze the mobile app of users when viewing that particular channel. 

Mattermost iOS app fails to properly validate the server certificate while initializing the TLS connection allowing a network attacker to intercept the WebSockets connection.

Mattermost Sever fails to redact the DB username and password before emitting an application log during server initialization. 

Mattermost fails to check the "Show Full Name" setting when rendering the result for the /plugins/focalboard/api/v2/users API call, allowing an attacker to learn the full name of a board owner.

A missing permissions check in Mattermost Playbooks in Mattermost allows an attacker to modify a playbook via the /plugins/playbooks/api/v0/playbooks/[playbookID] API.

A missing permissions check in the /plugins/playbooks/api/v0/runs API in Mattermost allows an attacker to list and view playbooks belonging to a team they are not a member of.

A denial-of-service vulnerability in Mattermost allows an authenticated user to crash the server via multiple large autoresponder messages.