I won’t assume it’s automatically child abuse.
There are photos of my own son dressed as a girl at around the same age. He put on his sisters dress because he thought it was funny, and we thought it was pretty cute.
But I certainly think it’s something questions need to be asked about, given the situation here.
And I don’t think much of the judgement of the foster parents in putting these pictures online if it was something innocent, because they should have the brains to realise what it might look like in the circumstances and not be stupid enough to risk that.