An issue was discovered in Mattermost Server before 5.2.2, 5.1.2, and 4.10.4. It allows remote attackers to cause a denial of service (memory consumption) via crafted image dimensions.
An issue was discovered in Mattermost Server before 5.2 and 5.1.1. Authorization could be bypassed if the channel name were not the same in the params and the body.