YesWiki before 4.6.7 contains a stored cross-site scripting vulnerability in the Bazar FileField, which validates only the upload's file extension and never calls HtmlPurifierService::cleanFile, so SVG files are stored verbatim and served inline as image/svg+xml. Authenticated users can submit entries via POST /api/entries/{formId} with SVG files containing script that executes in the wiki origin when the file is opened, enabling administrator session or account compromise.