As of today, I am getting a hex string delimited by colons prepended to the red pop-up messages. The only place I've seen this so far is Tower of Frozen Shadow: Umbral Halls, sixth floor, but that's probably because that's the first place I've played today that had red pop-up messages (boss emotes etc) to show me. The bug is that the messages are prefixed with a hex identifier that the devs obviously didn't intend to be displayed. I don't have a specific one to quote, they go by too fast, so for a message such as "The Boss is getting Really Pissed", you instead get a popup that looks like this: :e335a223bc32435:The Boss is getting Really Pissed
PS: The reason I'm posting here rather than simply submitting an in-game bug is I suspect this is global (for red boss emotes) everywhere, and don't see a need to inundate them with duplicate bug reports. I If you are seeing this in other places/dungeons, please add a "me too" post. If I don't see a few of those, I'll assume this is somehow unique to ToFS and submit an in-game bug.