The link "mass delete" on Special:Contributions does not work properly. The parameter "target" is ignored. e.g. https://www.mediawiki.org/w/index.php?title=Special:Nuke&target=Shirayuki
Topic on Project:Current issues
FuzzyBot is actually a piece of MediaWiki software--it's not an actual user or bot (e.g., if you block it, it can still edit).
It is just one example of users.
Special:Nuke accepts "wpnuke-target" not "target", but Special:Contributions passes "target".
task T158502, apparently will be fixed during Monday.