A bug report from wikimedia.org, https://www.mediawiki.org/wiki/Topic:U12oukyg4w1h6tnx
"I have the Wikipedia mobile app installed on both my phone and my tablet (both Android devices), and I have seen a significant uptick in the last couple of months of notifications of a multitude of failed login attempts that seem to coincide with my having opened the app, perhaps with a less-than-reliable internet connection. Is this a known issue?"
I asked him to confirm whether these are failed attempt notifications, or successful from an unfamiliar device. He says he's getting failed notices, but successful seems like it would make more sense...