Semantic MediaWiki is a free, open-source extension to MediaWiki that lets users store and query data within the wiki's pages. In versions 7.0.0 through 7.1.0, Special:Ask accepts a cursor query parameter for keyset pagination (added in 7.0.0). The token is decoded by CursorEncoder, which is an unsigned base64url-encoded JSON blob, so its contents are fully attacker-controlled. When the cursor's sort anchor does not match the request's sort= / order=, QueryCreator::applyCursorIfRequested() builds an error message by interpolating the attacker-controlled sort_prop / sort_order values into a raw string via Query::addErrors(). Unlike SMW's message-key errors, this raw string bypasses the message layer's sanitization (ProcessingErrorMsgHandler::normalizeAndDecodeMessages() passes a non-key, non-encoded string through unchanged). ErrorWidget::queryError() then assembles the errors and passes them to Html::errorBox(), whose first argument is emitted as raw HTML. The result is a reflected cross-site scripting vulnerability: a crafted cursor token containing markup in sort_prop (or sort_order) executes script in the victim's browser on the wiki origin. No authentication or special permission is required. The payload is delivered via a crafted link. Version 7.2.0 contains a fix.