If 127.0.0.1 is autoblocked, [[Special:Contributions/127.0.0.1]] shows a link "change block" instead of "block", though there's no block log shown. However imagine there's only one autoblock listed in Special:BlockList, or a user is newly blocked with autoblock enabled, a malicious sysop may check contribution pages of all IP addresses for this link text change from "block" to "change block", and associate this IP with the user triggering this autoblock.
Version: unspecified
Severity: normal