matrix-synapse vulnerable to improper validation of receipts allows forged read receipts
ImpactUsers were able to forge read receipts for any event (if they knew the room ID and event ID). Note that the users were not able to view the events, but simply mark it as read. This could be confusing as clients will show the event as read by the user, even if they are not in the room.Patcheshttps://github.com/matrix-org/synapse/pull/16327WorkaroundsThere is no workaround.