Last modified: 2014-11-17 09:21:26 UTC
https://ru.wikipedia.org/wiki/%D0%EE%F1%F2_%F7%E5%EB%EE%E2%E5%EA%E0 (title encoded in WIN1251) has <link rel="canonical" href="http://ru.wikipedia.org/wiki/%D0%EE%F1%F2_%F7%E5%EB%EE%E2%E5%EA%E0" /> while http://ru.wikipedia.org/wiki/%D0%A0%D0%BE%D1%81%D1%82_%D1%87%D0%B5%D0%BB%D0%BE%D0%B2%D0%B5%D0%BA%D0%B0 (same page ,title encoded in UTF-8) has <link rel="canonical" href="http://ru.wikipedia.org/wiki/%D0%A0%D0%BE%D1%81%D1%82_%D1%87%D0%B5%D0%BB%D0%BE%D0%B2%D0%B5%D0%BA%D0%B0" /> This results in the page featurng twice in search engines' index.
Change 151221 had a related patch set uploaded by MaxSem: Make sure canonical URLs are always in UTF-8 https://gerrit.wikimedia.org/r/151221