CVE-2026-32308: OneUptime: Stored XSS via Mermaid Diagram Rendering (securityLevel: "loose")

March 13, 2026 (updated March 16, 2026)

The Markdown viewer component renders Mermaid diagrams with securityLevel: "loose" and injects the SVG output via innerHTML. This configuration explicitly allows interactive event bindings in Mermaid diagrams, enabling XSS through Mermaid’s click directive which can execute arbitrary JavaScript. Any field that renders markdown (incident descriptions, status page announcements, monitor notes) is vulnerable.

References

github.com/OneUptime/oneuptime
github.com/OneUptime/oneuptime/releases/tag/10.0.23
github.com/OneUptime/oneuptime/security/advisories/GHSA-wvh5-6vjm-23qh
github.com/advisories/GHSA-wvh5-6vjm-23qh
nvd.nist.gov/vuln/detail/CVE-2026-32308

Code Behaviors & Features

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