Only a few days after the release of Patch 7.1, Teemo has been temporarily disabled due a serious bug with his invisibility mechanic. The bug allows Teemo to re-enter invisibility more quickly than intended, even while he is fighting other champions. You can see the bug in action here, via YouTube user Rainbow Gaming:
The bug relates to Teemo’s passive, which allows him to go invisible when standing still or in a bush. When Teemo attacks, he becomes visible again and isn’t supposed to be able to return to invisibility until he exits combat. With the bug, however, Teemo becomes invisible far too quickly after attacking from a bush, even while still in combat. This makes the already aggravating champion almost impossible to deal with.
Riot noticed the bug late Thursday night and disabled the champion until further notice. You can expect Teemo to be re-enabled again some time over the next few days.