http://xn--kbenhavn-54a.eu is the decoded version of the internationalized domain name http://københavn.eu . Steps to reproduce:

1. Add \bxn--kbenhavn-54a\.eu\b to the local spam blacklist (example).
2. Add a link to http://københavn.eu on any wiki page (example). This link addition is not blocked.
3. Replace \bxn--kbenhavn-54a\.eu\b with \bkøbenhavn\.eu\b on the same spam blacklist (example).
4. Add a link to http://xn--kbenhavn-54a.eu on any wiki page (example). This link addition is not blocked.

Both decoded and encoded domain names in links should be tested against the spam blacklist.

MediaWiki version: 1.27.0-wmf.17 (rMWd511973bb2ba) 03:00, 18 March 2016