If you open the problemset status page, you’ll notice something strange. Many users with randomly generated names (basically random letters and numbers) have made a huge number of submissions. These submissions are mostly for recent problems, one by one, and almost all use Python 3. If you click on any of them, you’ll see that they submit about once every two minutes. The code in these submissions looks very similar, so I suspect these users are actually AIs.

Here is a screenshot of a problems.

And another screenshot of a user.