Mattermost Desktop

Mattermost Desktop App versions <=6.1 5.5.13.0 fail to account for attempting to open extremely long URLs in the Mattermost Desktop App which allows a malicious server owner to crash the application via including a script to call window.open on a very large URL. Mattermost Advisory ID: MMSA-2026-00652Show less

Mattermost Desktop App versions <=6.1 5.5.13.0 fail to restrict the allow list of domains to which NTLM credentials were forwarded to in the Mattermost Desktop App which allows any user on a server without the image proxy enabled to intercept other users credentials via embedding an image that routes to an external web server. Mattermost Advisory ID: MMSA-2026-00651Show less

Mattermost Desktop App versions <=6.1 6.0.1 5.4.13.0 fail to prevent server-rendered content from closing an underlying application view in the Mattermost Desktop App which allows a malicious server or plugin to crash the desktop client via invoking {{window.close()}} in the renderer context, leading to a denial of service condition at the client level. Mattermost Advisory ID: MMSA-2026-00633Show less

Mattermost Desktop App versions <=6.1 6.0.1 5.4.13.0 fail to prevent an invalid URL from loading in a pop-up window in the Mattermost Desktop App which allows a malicious server owner to repeated crash the application via calling {{window.open('javascript:alert()');}}. Mattermost Advisory ID: MMSA-2026-00618Show less

Mattermost Desktop App versions <=5.13.3 fail to attach listeners restricting navigation to external sites within the Mattermost app which allows a malicious server to expose preload script functionality to untrusted servers via having a user open an external link in their Mattermost server. Mattermost Advisory ID: MMSA-2026-00596Show less

Mattermost Desktop App versions <=6.0 6.2.0 5.2.13.0 fail to validate help links which allows a malicious Mattermost server to execute arbitrary executables on a user’s system via the user clicking on certain items in the Help menu Mattermost Advisory ID: MMSA-2026-00577Show less

Mattermost Desktop App versions <6.0.0 fail to enable the Hardened Runtime on the Mattermost Desktop App when packaged for Mac App Store which allows an attacker to inherit TCC permissions via copying the binary to a tmp folder.Show less

Mattermost Desktop App versions <6.0.0 fail to sanitize sensitive information from Mattermost logs and clear data on server deletion which allows an attacker with access to the users system to gain access to potentially sensitive information via reading the application logs.Show less

Mattermost Desktop App versions <=5.13.0 fail to manage modals in the Mattermost Desktop App that stops a user with a server that uses basic authentication from accessing their server which allows an attacker that provides a malicious server to the user to deny use of the Desktop App via having the user configure the malicious server and forcing a modal popup that cannot be closed.Show less

Mattermost Desktop App versions <= 5.13.0 fail to validate URLs external to the configured Mattermost servers, allowing an attacker on a server the user has configured to crash the user's application by sending the user a malformed URL.Show less

Mattermost Desktop App versions <=5.8.0 fail to specify an absolute path when searching the cmd.exe file, which allows a local attacker who is able to put an cmd.exe file in the Downloads folder of a user's machine to cause remote code execution on that machine.Show less

Mattermost Desktop App versions <=5.7.0 fail to correctly prompt for permission when opening external URLs which allows a remote attacker to force a victim over the Internet to run arbitrary programs on the victim's system via custom URI schemes.Show less