In the land of tabloid whispers, Fox, 22, has had her sights locked on the also-taken Zac Efron, 21, for some time now. Supposedly, Megan is hellbent on cracking the High School Musical stud's proverbial locker combination.

The sexy flirtation between the two Hollywood "It" kids began at the Golden Globes two weeks ago, says Star.

When Megan showed up alone on the red carpet, she was asked where her boyfriend, 35-year-old Green, was.

"He doesn't want to be here," she told reporters. "He doesn't want to be my date. He's a man. He has an ego... I don't think he cares."

Later at the Globes after-party at the Sunset Towers Hotel, Star claims Fox swooped down on Efron, despite the fact that he was with girlfriend Vanessa Hudgens.

"The spark between Zac and Megan was obvious to anyone there," says an eyewitness.

"There were times when they seemed lost in conversation together, while Vanessa stood by like a sulking little girl. Vanessa is lovely, but Megan is considered one of the hottest women on the planet."

But while Megan may be one hot fox, V-Hud, 20, shouldn't be underestimated.

After all, she has a wide array of toys in her arsenal, and she's not afraid to use them.