LOS ANGELES, CA - FEBRUARY 09: Singers Katy Perry (L) and Miley Cyrus arrive at the 55th Annual GRAMMY Awards Pre-GRAMMY Gala
Lester Cohen/WireImage

Not long after Katy Perry's rumored split with on-again, off-again boyfriend John MayerMiley Cyrus slapped Perry with the following tweet: "Girl if ur worried abt where tongues have been, good thing ur ex boo is ur EX BOO cause we ALL know where THAT been." In case you didn't get it, she's pointing out that Mayer's hooked up with approximately 40% of the women he's ever met. 

Okay, so here's the deal. A few weeks ago, Katy Perry was in the front row of Miley CyrusBangerz concert in Los Angeles. While Cyrus was singing "Adore You," she bent in for an open-mouth kiss, but Perry settled for a kiss on the mouth. Perry gave an interview to an Australian radio station earlier this week about the kiss, saying, "I just walked up to her to give her like a friendly girly kiss, you know, as girls do. Then she like tried to move her head and go deeper and I pulled away."

Perry continued: "God knows where that tongue has been. We don't know! That tongue is so infamous!" Those comments made their way across the Pacific to Cyrus, who today jabbed back at her friend by dissing her Lothario ex-boyfriend John Mayer.

The "Dark Horse" singer took the jab in stride, slapping back at Miley later that day on Twitter: "Oooo gurrrl I'm gonna give you the BIGGEST spanking when I see you in the UK."