Matrix Synapse before 1.5.0 mishandles signature checking on some federation APIs. Events sent over /sendjoin, /sendleave, and /invite may not be correctly signed, or may not come from the expected servers.
{ "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro", "ubuntu_priority": "medium", "binaries": [ { "matrix-synapse": "0.24.0+dfsg-1ubuntu0.1~esm1" } ] }
{ "availability": "No subscription required", "ubuntu_priority": "medium", "binaries": [ { "matrix-synapse": "1.11.0-1" } ] }