Mattermost versions 10.4.x <= 10.4.1, 9.11.x <= 9.11.7, 10.3.x <= 10.3.2, 10.2.x <= 10.2.2 fail to properly validate board blocks when importing boards which allows an attacker could read any arbitrary file on the system via importing and exporting a specially crafted import archive in Boards.
Mattermost versions 10.4.x <= 10.4.1, 9.11.x <= 9.11.7, 10.3.x <= 10.3.2, 10.2.x <= 10.2.2 fail to properly validate input when patching and duplicating a board, which allows a user to read any arbitrary file on the system via duplicating a specially crafted block in Boards.
An issue was discovered in Mattermost Desktop App before 4.3.0 on macOS. It allows dylib injection.
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.