Recently, the Finder has asked me for a password whenever I move a file to the trash. I get the message, "Finder wants to move 'filename' to the trash. Enter your password to allow this". I checked permissions on ~/.Trash, and it belongs to me/staff with drwx------ permissions, as expected. This happens with any file I try to delete, and I have full permissions on the files I'm deleting. When I enter the password, the file is moved to the trash (and not immediately deleted) as normal.
This is on Mojave 10.14.6, and it started happening after I installed security update 2021-003 (though I don't remember if it started happening immediately after that).
Note that I can move files to the trash from a command line.
mv blah.txt ~\.Trash works just fine (no sudo needed). It's only when I drag a file to the trash that I have problems.