Fix stored XSS in PageHead via HtmlSanitizer allowlist#2408
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Fix stored XSS in PageHead via HtmlSanitizer allowlist#2408
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…allowlist Agent-Logs-Url: https://github.com/fluentcms/FluentCMS/sessions/1651a529-c67c-468a-bb04-c0561e9d436c Co-authored-by: pournasserian <24959477+pournasserian@users.noreply.github.com>
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[WIP] Fix reflected XSS vulnerability in FluentCMS admin page
Fix stored XSS in PageHead via HtmlSanitizer allowlist
Mar 30, 2026
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The page
Headsettings field was rendered verbatim as aMarkupString, allowing any admin to store arbitrary<script>tags that execute for all page visitors. TheGoogleTagsIdsetting had the same issue — injected directly into generated<script>tags without validation.Changes
HtmlSanitizer(Ganss.Xss 9.0.892) added toFluentCMS.Web.UIPageHead.razor.cspermitting only safe head-section elements (<meta>,<link>,<style>,<noscript>) and their expected attributes; applied before renderingHeadcontent asMarkupString:GoogleTagsIdvalidation — strict^[A-Za-z0-9\-]+$regex check before embedding the value in generated script tags; returns empty string on mismatch