Dua Lipa's Security Slaps Away Fan's Hand As It Inches Toward Her Butt, On Video

Dua Lipa’s hot, no cap ... but try anything funny and you’re getting schooled -- just ask the fan who learned the hard way!

Catch the clip ... Dua was killing it at the Kia Forum in L.A. this weekend, posing for fan pics when one dude got way too familiar, sliding his hand near her booty -- before security delivered an instant rear-end reality check.

The whole crowd saw it go down and couldn’t help but laugh out loud when security smacked his hand away. Oof, instant cringe!

Dua didn’t even notice the near-bum grab -- she was too in the zone, snapping pics like a pro ... but the clip went viral fast, leaving fans totally horrified.