After another visit to the launcher, I saw that the latest version was replaced with a modified OptiFine. This isn't the first time this has happened, and I didn't put any effort into it (other than installing OptiFine). However I still can't configure or delete this version.
Translate (with GT):
Последний снапшот - Last snapshot
Последняя версия - Last version
Удалить - Delete
Yep we are aware of this issue happening occasionally. We have a fix for it in the works!