Fil (it's dh step dad) offered to help decorate our living room. So I said yes since dh has dyspraxia and can't really help. When I was climbing up the ladder Fil smacked / spanked me on the bottom. I just froze for a second as I was speechless and then just carried on. I didn't say anything because I was shocked and am too socially anxious to say anything.
i told dh, and he didn't say much other than if it happens again he will say something.
AIBU to be annoyed and think it's a violation of my personal space, and very inappropriate of Fil?