The pair locked lips while Katy was sitting in the front row at Miley's concert at the Staples Centre in Los Angeles.
'Roar' singer Katy has since said that she had to pull away from Miley, and claimed during a TV interview in Australia: "I just walked up to her to give her a friendly girly kiss. You know as us girls do.
"And then she like tried to move her head and go deeper and I pulled away. God knows where that tongue has been!"
But last night (6 March), Miley posted a picture of Katy and in what could possibly be reference to Katy's on-off romance with John Mayer, Miley said: "Girl if ur worried abt where tongues have been good thing ur ex boo is ur EX BOO cause we ALL know where THAT [tongue] been."
'Wrecking Ball' singer Miley later made a joke of the situation, tweeting: "Dontchyouuuu act like you didn't lurvvvvv it @katyperry," with a tongue, heart and kiss icon.
It appears 29-year-old Katy saw the funny side as she soon replied: "@MileyCyrus Oooo gurrrl I'm gonna give you the BIGGEST spanking when I see you in the UK bb!"
Popstar Katy has so far remained tight-lipped on her current relationship status with John following recent reports that they split in February.
Miley's mammoth tour kicked off last month, while Katy's 'Prismatic World Tour' will kick off in May.
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Watch Miley's music video for 'Adore You' below: