Once, Katy Perry and Taylor Swift were friends. 

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Getty Images
In 2010

Then, they weren't, because of backup dancer drama, as the tabloid tales go. "Bad Blood" was written; indirect shade was thrown in interviews and tweets. Time passed, and everyone (probably) moved on. Katy invited Taylor to her pre-Grammys-Spotify party in January; Katy attended the Met Gala Taylor co-hosted in May. 

But someone out there isn't over it, and they made it known last night when they hacked Katy's Twitter account and tweeted "miss u baby @taylorswift13" among other things (they also posted a link to an unreleased Katy song on their own account that was taken down). 

E! grabbed screenshots before the tweets were deleted:

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E! News/Twitter

Katy has not commented on the incident. She chose to do this instead: