This question already has an answer here:
On a random online quiz, I was presented with the following one:
Elles se sont ____ dans leur malheur.
The two options were complu and complues (past participle of complaire). I picked complues and was told that complu was correct.
I am very confused because agreement of past participle with the auxiliary verb être is very obvious to me.
I have already read this answer and I think se (elles) is the direct object (there's nothing else that could serve as the object). Am I wrong here or elsewhere?