Report: Complete Guide to CVE-2026-44429 - MCP Registry: Stored XSS in catalogue UI via attribute-quote breakout in publish...
CVE ID :CVE-2026-44429 Published : May 14, 2026, 9:16 p.m. | 1 hour, 20 minutes ago Description :The MCP Registry provides MCP clients with a list of MCP servers, like an app store for MCP servers. Prior to 1.7.7, the public catalogue UI served at GET / (file internal/api/handlers/v0/ui_index.html) is vulnerable to stored cross-site scripting via the server.websiteUrl field of any published server.json. Server-side validation in internal/validators/validators.go (validateWebsiteURL) only checks that the URL parses, is absolute, and uses the https scheme; it does not reject quote characters. Client-side, the value is interpolated into a double-quoted href attribute via innerHTML, using a homegrown escapeHtml helper that performs the standard textContent → innerHTML round-trip. Per the HTML serialisation algorithm, that round-trip encodes only &, <,and U+00A0 inside text nodes — it does not encode