Is "@mcp-b/webmcp-local-relay" on MCP Registry Safe to Install?
Local MCP relay for browser WebMCP tools via embed iframe and localhost WebSocket
Risk Assessment
Analyzed159 security findings detected across all analyzers
MCP server analyzed for tool poisoning, prompt injection, and data exfiltration
Severity Breakdown
Finding Categories
YARA Rules Matched
11 rules(50 hits)MCP Server Analysis
MCP servers expose tools and resources to AI assistants. Unlike browser extensions, they run as standalone processes with direct system access. Tool definitions are analyzed for prompt injection, data exfiltration, and tool poisoning patterns.
About This Extension
Detailed Findings
65 totalYARA Rule Matches
11 rulesIndicators of Compromise
Network indicators, suspicious strings, and potential IoCs extracted during analysis
All Indicators · 92
detected Domain: this.host XIOC detected Domain: this.host
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detected Domain: e.host XIOC detected Domain: e.host
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detected URL: https://github.com/WebMCP-org/npm-packages.git XIOC detected URL: https://github.com/WebMCP-org/npm-packages.git
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detected URL: https://app1.com,https://app2.com XIOC detected URL: https://app1.com,https://app2.com
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detected URL: https://webmachinelearning.github.io/webmcp/) XIOC detected URL: https://webmachinelearning.github.io/webmcp/)
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detected URL: https://github.com/webmachinelearning/webmcp) XIOC detected URL: https://github.com/webmachinelearning/webmcp)
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detected URL: https://github.com/modelcontextprotocol/mcpb) XIOC detected URL: https://github.com/modelcontextprotocol/mcpb)
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detected URL: https://docs.claude.com/en/docs/claude-code/plugins/build-a-plugin) XIOC detected URL: https://docs.claude.com/en/docs/claude-code/plugins/build-a-plugin)
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detected URL: https://docs.claude.com/en/docs/claude-code/plugins/distributing-plugins) XIOC detected URL: https://docs.claude.com/en/docs/claude-code/plugins/distributing-plugins)
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detected URL: https://docs.claude.com/en/docs/claude-code/skills) XIOC detected URL: https://docs.claude.com/en/docs/claude-code/skills)
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detected URL: https://cdn.jsdelivr.net/npm/@mcp-b/webmcp-local-relay@latest/dist/browser/embed.js XIOC detected URL: https://cdn.jsdelivr.net/npm/@mcp-b/webmcp-local-relay@latest/dist/browser/embed.js
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detected URL: https://cdn.jsdelivr.net/npm/@mcp-b/global@latest/dist/index.iife.js XIOC detected URL: https://cdn.jsdelivr.net/npm/@mcp-b/global@latest/dist/index.iife.js
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detected URL: https://github.com/webmachinelearning/webmcp/blob/main/docs/proposal.md) XIOC detected URL: https://github.com/webmachinelearning/webmcp/blob/main/docs/proposal.md)
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detected URL: https://github.com/WebMCP-org/npm-packages/releases) XIOC detected URL: https://github.com/WebMCP-org/npm-packages/releases)
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detected URL: https://myapp.com XIOC detected URL: https://myapp.com
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detected Domain: t.name XIOC detected Domain: t.name
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detected Domain: allsources.map XIOC detected Domain: allsources.map
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detected Domain: dsr.js.map XIOC detected Domain: dsr.js.map
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detected Domain: registry.npmjs.org XIOC detected Domain: registry.npmjs.org
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detected Domain: build-mcpb.sh XIOC detected Domain: build-mcpb.sh
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detected URL: https://github.com/WebMCP-org/npm-packages XIOC detected URL: https://github.com/WebMCP-org/npm-packages
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detected URL: https://img.shields.io/npm/v/@mcp-b/webmcp-local-relay?style=flat-square)](https://www.npmjs.com/package/@mcp-b/webmcp-local-relay) XIOC detected URL: https://img.shields.io/npm/v/@mcp-b/webmcp-local-relay?style=flat-square)](https://www.npmjs.com/package/@mcp-b/webmcp-local-relay)
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detected URL: https://registry.npmjs.org/ XIOC detected URL: https://registry.npmjs.org/
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detected Domain: tool.name XIOC detected Domain: tool.name
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detected Domain: tool.sources.map XIOC detected Domain: tool.sources.map
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detected Domain: parsed.data XIOC detected Domain: parsed.data
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detected Domain: value.map XIOC detected Domain: value.map
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detected Domain: left.name XIOC detected Domain: left.name
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detected Domain: right.name XIOC detected Domain: right.name
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detected Domain: this.off XIOC detected Domain: this.off
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detected Domain: server.off XIOC detected Domain: server.off
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detected Domain: resolved.tool.name XIOC detected Domain: resolved.tool.name
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detected Domain: relaymsg.data XIOC detected Domain: relaymsg.data
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detected Domain: parsedmessage.data XIOC detected Domain: parsedmessage.data
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detected Domain: message.tools XIOC detected Domain: message.tools
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detected Domain: ws.off XIOC detected Domain: ws.off
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detected Domain: tools.map XIOC detected Domain: tools.map
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detected Domain: rankedproviders.map XIOC detected Domain: rankedproviders.map
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detected Domain: primaryprovider.tool.name XIOC detected Domain: primaryprovider.tool.name
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detected Domain: b.name XIOC detected Domain: b.name
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detected Domain: provider.tool.name XIOC detected Domain: provider.tool.name
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detected Domain: providers.map XIOC detected Domain: providers.map
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detected URL: https://github.com/WebMCP-org/npm-packages#readme XIOC detected URL: https://github.com/WebMCP-org/npm-packages#readme
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detected Domain: inbound.name XIOC detected Domain: inbound.name
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detected Domain: inputschemaparsed.data XIOC detected Domain: inputschemaparsed.data
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detected Domain: outputschemaparsed.data XIOC detected Domain: outputschemaparsed.data
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detected Domain: annotationsparsed.data XIOC detected Domain: annotationsparsed.data
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detected Domain: normalizedparsed.data XIOC detected Domain: normalizedparsed.data
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detected Domain: this.name XIOC detected Domain: this.name
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detected Domain: this.now XIOC detected Domain: this.now
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detected Domain: i.tools XIOC detected Domain: i.tools
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detected Domain: options.host XIOC detected Domain: options.host
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detected Domain: cli.js.map XIOC detected Domain: cli.js.map
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detected Domain: index.d.ts.map XIOC detected Domain: index.d.ts.map
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detected Domain: myapp.example.com XIOC detected Domain: myapp.example.com
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detected Domain: parsed.host XIOC detected Domain: parsed.host
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detected Domain: options.now XIOC detected Domain: options.now
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detected Domain: n.host XIOC detected Domain: n.host
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detected Domain: t.host XIOC detected Domain: t.host
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detected Domain: s.data XIOC detected Domain: s.data
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detected Domain: r.host XIOC detected Domain: r.host
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detected Domain: t.tools XIOC detected Domain: t.tools
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detected Domain: o.host XIOC detected Domain: o.host
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detected Domain: r.data XIOC detected Domain: r.data
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detected Domain: e.name XIOC detected Domain: e.name
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detected Domain: i.search XIOC detected Domain: i.search
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detected Domain: t.data XIOC detected Domain: t.data
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detected Domain: websocket.open XIOC detected Domain: websocket.open
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detected Domain: window.location.search XIOC detected Domain: window.location.search
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detected Domain: e.tools XIOC detected Domain: e.tools
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detected Domain: message.data XIOC detected Domain: message.data
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detected IP: 127.0.0.1 XIOC detected IP: 127.0.0.1
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detected Domain: readme.md XIOC detected Domain: readme.md
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detected Domain: proposal.md XIOC detected Domain: proposal.md
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detected Domain: app1.com XIOC detected Domain: app1.com
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detected Domain: app2.com XIOC detected Domain: app2.com
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detected Domain: skill.md XIOC detected Domain: skill.md
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detected Domain: date.now XIOC detected Domain: date.now
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detected IP: ::1 XIOC detected IP: ::1
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detected Domain: github.com XIOC detected Domain: github.com
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detected Domain: img.shields.io XIOC detected Domain: img.shields.io
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detected Domain: cdn.jsdelivr.net XIOC detected Domain: cdn.jsdelivr.net
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detected Domain: myapp.com XIOC detected Domain: myapp.com
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detected Domain: webmachinelearning.github.io XIOC detected Domain: webmachinelearning.github.io
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detected Domain: docs.claude.com XIOC detected Domain: docs.claude.com
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detected URL: https://myapp.example.com]', XIOC detected URL: https://myapp.example.com]',
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detected URL: https://myapp.example.com] XIOC detected URL: https://myapp.example.com]
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detected URL: https://cdn.jsdelivr.net/npm/@mcp-b/webmcp-local-relay/dist/browser/widget.html XIOC detected URL: https://cdn.jsdelivr.net/npm/@mcp-b/webmcp-local-relay/dist/browser/widget.html
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detected URL: https://github.com/vercel-labs/agent-skills) XIOC detected URL: https://github.com/vercel-labs/agent-skills)
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detected URL: https://your-widget-domain.example XIOC detected URL: https://your-widget-domain.example
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detected Domain: www.npmjs.com XIOC detected Domain: www.npmjs.com
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detected URL: https://github.com/WebMCP-org/npm-packages/issues XIOC detected URL: https://github.com/WebMCP-org/npm-packages/issues
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Security Analysis Summary
Security Analysis Overview
@mcp-b/webmcp-local-relay is a mcp extension published by miguelspizza. Version 2.2.0 has been analyzed by the Risky Plugins security platform, receiving a risk score of 100/100 (CRITICAL risk) based on 159 security findings.
Risk Assessment
This extension presents critical security risk. Severe issues were detected, potentially including malware indicators, exposed secrets, or dangerous behaviors. Installation is strongly discouraged until these issues are addressed.
Findings Breakdown
- Critical: 2 finding(s)
- High: 52 finding(s)
- Medium: 98 finding(s)
What Was Analyzed
The security assessment covers multiple analysis categories:
- Malware Detection: YARA rule matching against 2,400+ malware signatures
- Secret Detection: Scanning for exposed API keys, tokens, and credentials
- Static Analysis: Code-level security analysis for common vulnerability patterns
- Network Analysis: Detection of suspicious network communications and endpoints
- Obfuscation Detection: Identification of code obfuscation techniques
Developer Information
@mcp-b/webmcp-local-relay is published by miguelspizza on the mcp marketplace.
Recommendation
This extension is not recommended for installation without thorough manual review. Consider alternatives with lower risk scores, or contact the developer to address the identified security concerns.
Source Code Not Available
Source code is not available for this version of the extension.
Frequently Asked Questions
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