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.
Selena quickly deactivated her account after the hack.