Selena Gomez's Instagram Gets Hacked, Justin Bieber Nudes Posted

Selena Gomez's Instagram account just got hacked ... and whoever's behind it immediately posted nude photos of her ex, Justin Bieber.

A post from Selena's official IG account went up Monday showing 3 paparazzi pics of Bieber flashing his penis ... with a caption that read "LOOK AT THIS N***A LIL SHRIMPY."

The alleged hackers included their IG handles and claimed they "run da scene."

The accounts appear to belong to 3 random Internet trolls who only have a handful of posts, and thousands of followers between them.