The Matrix team has just released synapse 1.19.2 , an emergency security release. Upgrading is encouraged as soon as possible.
The release fixes an issue where a broken or malicious homeserver can make a room unjoinable by sending malformed events into the room.
(In reply to Denis Kasak from comment #0)
I've already submitted an updated port at . Seems like you were a bit faster in submitting this bug than I was at submitting the patch. :D
Ah, good to know, I was in the process of writing a patch too. :D Thanks!
I'll close this bug as a duplicate of yours then.
*** This bug has been marked as a duplicate of bug 249375 ***