The "I Knew You Were Trouble" singer dropped the F-bomb at MTV's Video Music Awards on Sunday when her ex-boyfriend Harry Styles and One Direction band member took the stage to present the night's first award for best pop video. The band rambled about being British and the best fans being in New York, where the show took place this year. That's when the audience camera cut to Swift. Swift, 23, who isn't shy about telling people how she really feels, was caught saying "shut the ... up" to bestie Selena Gomez, after Zayn Malik's part of the intro. Really mature. You'd think her own spotty history with this award show would have taught her a thing or two, but it seems that the "22" singer is just emboldened by the show's "anything can happen" vibe. Surprisingly enough, the band presented the award to pal Gomez, who took the stage and sweetly greeted the band as she accepted her Moonman. And that was the end of that, right? When Swift accepted her award for female video later in the show, she didn't hold back about her inspiration for her hit "I Knew You Were Trouble." After thanking her fans, video director and costar, Swift took aim at her ex again. "I also want to thank the person who inspired this song, who knows exactly who he is," she said, "because now I got one of these. Thank you so much! And the camera cut to Styles, who clapped for her, smugly chewed his gum and took notice that cameras were focused on his reaction. Way to play it cool. Some reports also said the song could have reportedly been written about her fling with actor Jake Gyllenhaal in 2010. But there are so many exes in her past, it's getting really difficult to keep track. Swift and Styles briefly dated last year before splitting this January. Soon after, she took swipes at him at the Grammy Awards and the Brit Awards too. In the VMA pre-show, Swift revealed to MTV VJ Sway that she had already started working on her next album (can we expect another call-out song?). And just last week, Styles admitted that he'd be OK with Swift writing an inevitable breakup song about him because he thought she was "a great songwriter." Too bad she already has...