Language of language names in the language selector?

Imagine a site that's available in multiple languages. The language is detected automatically by looking at the IP or the browser header. But that's not bulletproof, so a few users might end up on a page in language they don't understand.

I am wondering what the best way is to present the language selection?

mockup

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Q: Should the languages in the language selection be listed

  1. translated into current language, used to display the site in (good if the detected language was correct)?
  2. native name of the language, so everybody looking for their language could see it in the very same language (good if the detected language was not correct and users don't know the current language)?
  3. always in English assuming most users would understand this?

Feel free to add if I missed something!