Katy Perry's Twitter account was hacked.
Which is a problem, because almost 90 million people follow Katy Perry on Twitter, making the pop singer the most followed person in the world.
How do we know Katy was hacked?
She said something nice about Taylor Swift.
It could have been worse. Imagine if the hacker had tweeted a malicious link instead of a juvenile message to Perry's arch-rival.
Stay safe folks!