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Medium · 5.4 CVE-2026-77272 EUVD-2026-84749GHSA-g2r2-3j32-j27xPYSEC-2026-4093

MCP Atlassian: Reflected XSS in OAuth Setup Callback Handler

Published Sep 22, 2026 · Updated Sep 23, 2026 · Assigned by GitHub_M

Description

MCP Atlassian is a Model Context Protocol (MCP) server for Atlassian products (Confluence and Jira). Prior to 0.22.0, the OAuth error query parameter is passed to CallbackHandler._send_response in oauth_setup.py and interpolated into an HTML page without escaping. A crafted authorization callback can inject markup or script that executes in the browser of a user completing the OAuth flow. This issue is fixed in version 0.22.0.

Affected products

VendorProductAffectedFixed
sooperset mcp-atlassian < 0.22.0 —

Affected packages

EcosystemPackageAffectedFixedRecord
PyPI mcp-atlassian < 0.22.0 0.22.0 GHSA-g2r2-3j32-j27x

References