The actress celebrated her birthday with Efron and a group of friends in Malibu, California on Saturday (02Jul11), but party photos of the two stars led to websites posing questions about the relationship.
Gossip blogger PerezHilton.com posted a series of snaps of the stars looking intimate on his site on Tuesday (05Jul11), but the pictures were quickly taken down.
And now Tisdale has spoken out to defend the images and confirm she's still dating longtime boyfriend Scott Speer.
In a post on her Twitter.com page, she writes, "Don't believe all pictures. People r (are) gonna come up with stuff to say bc (because) it sells! I had such a great birthday party with my friends, Family, and BOYFRIEND Scott. I will not let stupid rumors ruin all the fun we had!"
Meanwhile, Efron has been single since splitting from longtime girlfriend Vanessa Hudgens, who is also one of the hunk's former High School Musical co-stars.