The Matrix specification before 1.16 (i.e., with a room version before 12 and State Resolution before 2.1) has deficient state resolution.
Exploitability
AV:NAC:HPR:LUI:NScope
S:CImpact
C:NI:HA:L7.1/CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:H/A:LOther