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

An information exposure vulnerability has been found, the exploitation of which could allow a remote user to retrieve sensitive information stored on the server such as credential files, configuration files, application files, etc., simply by appending any of the following parameters to the end of the URL: %00 %0a, %20, %2a, %a0, %aa, %c0 and %ca.

Stored XSS vulnerability. This vulnerability could allow an attacker to store a malicious JavaScript payload via GET and POST methods on multiple parameters in the MailAdmin_dll.htm file.

Path traversal vulnerability whose exploitation could allow an authenticated remote user to bypass SecurityManager's intended restrictions and list a parent directory via any filename, such as a multiple ..%2F value affecting the 'dodoc' parameter in the /MailAdmin_dll.htm file.

Cross-Site Request Forgery (CSRF) vulnerability in Cimatti Consulting WordPress Contact Forms by Cimatti plugin <= 1.6.0 versions.

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.