OK! Exclusive: Inside the Zac & Vanessa Split

Last week, when OKmagazine.com first reported the unfortunate news that High School Musical co-stars and offscreen sweethearts and had gone their separate ways (click for original story), the reasons behind the split were still vague. But now, after much investigation, OK! can report who did the dumping — and why.

"Zac ended it," an insider close to the pair reveals exclusively to OK!. And the reason? Not shockingly, the 19-year-old actor wasn't too happy when nude pics of his barely legal gal pal started popping up all over the internet.

But this isn't the first time Zac's turned his back on the gorgeous brunette. For all the gory details about their roller coaster relationship, and why friends think this isn't the last time they'll split, check out the new issue of OK! — on sale everywhere Thursday.