An issue was discovered in Mattermost Server before 4.3.0, 4.2.1, and 4.1.2 when local storage for files is used. A System Admin can create arbitrary files.
Exploitability
AV:NAC:LPR:HUI:NScope
S:UImpact
C:NI:HA:N4.9/CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:H/A:N