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 5.12.0. Use of a Proxy HTTP header, rather than the source address in an IP packet header, for obtaining IP address information was mishandled.