Please use this thread going forward: Sims wear default underwear when naked | EA Forums - 4995249
I just noticed this in my game too. Guys are wearing the default CAS black underwear and the gals have the pink bra and underwear. I'm not using any CC in this household, this is the save I always play after big patches for this reason (removed mods/CC) So they've never worn CC outfits in this particular save. There's no reason for them to start wearing underwear now, other than it being related to the most recent patch.
I am having the same thing happen, also sometimes my sims hair changes in the shower and then changes back once they exit. All female sims wear the pink bra and underwear. It’s annoying I was hoping to find a fix
