This behavior was introduced in 25w15a.
The bug
So far, this issue has been reproduced with skeletons, wither skeletons, strays, bogged, and vindicators as the passengers, among others potentially. I have not lost a high-priority world, but this bug may still be dangerous.
A crash report with a vindicator as the test subject is attached, and the bug report should be public.
Steps to reproduce
Run the following command. It can brick a world, so be careful, please.
summon minecraft:turtle ~ ~ ~ {Passengers:[{id:"minecraft:vindicator"}]}
Observed behavior
The server will crash. On an integrated server, the game will close. On a dedicated server, the players will be disconnected.
Expected behavior
The server would run like normal, as was the case in versions prior to 25w15a.
Environment
Any
Can anyone else confirm? I was not sure what this glitch was for a bit?