MCP Inspector is Vulnerable to Potential Command Execution via XSS When Connecting to an Untrusted MCP Server
Published Sep 8, 2025 · Updated Nov 3, 2026
Original summary
Normalized public record · Updated Nov 3, 2026
MCP Inspector is Vulnerable to Potential Command Execution via XSS When Connecting to an Untrusted MCP Server
Publisher and source text is retained separately from QFinch interpretation.
QFinch assessment
An XSS flaw exists in the MCP Inspector local development tool when it renders a redirect URL returned by a remote MCP server. If the Inspector connects to an untrusted server, a crafted redirect can inject script into the Inspector context and, via the built-in proxy, be leveraged to trigger arbitrary command execution on the developer machine. Version 0.16.6 hardens URL handling/validation and prevents script execution.
Evidence: public source recordsAffected products
| Affected package, product or range | Fix status |
|---|---|
| Consult the referenced vendor advisory for affected versions. | Consult source advisory |
Matching a version is only one part of assessing exposure. QFinch has not assessed your environment on this public page.
Remediation
Apply the vendor-supported fixed release or mitigation, then verify the affected component is no longer reachable.
- Confirm the affected product and reachable code path exist in your environment.
- Apply the vendor-supported patch or mitigation from the primary advisory.
- Rescan the exact deployed revision and retain verification evidence.
Evidence coverage
- SSVC priority
- LOW
- Confidence
- Not available
- Aliases
- None reported
Scores appear only when corresponding evidence exists. Missing data is never interpreted as zero risk.
Sources and record history
Record history
Published Sep 8, 2025 · Last refreshed Nov 3, 2026