Mattermost versions 10.11.x <= 10.11.3, 10.5.x <= 10.5.11 fail to enforce access permissions on the Agents plugin which allows other users to determine when users had read channels via channel member objects
Exploitability
AV:NAC:HPR:LUI:RScope
S:CImpact
C:LI:NA:N3/CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:L/I:N/A:NOther