PYSEC-2026-2731 Open WebUI has stored XSS via unsanitized Office/Excel/DOCX file preview rendering ({@html} without DOMPurify)

Related advisory This advisory tracks a regression of the original Excel-preview XSS that was publicly disclosed and patched under GHSA-jwf8-pv5p-vhmc patched in v0.8.0. The same root cause — XLSX.utils.sheettohtml output rendered via @html excelHtml without DOMPurify — was reintroduced sometime...