Prompt injection in a public GitHub issue makes an MCP-connected agent leak private repository data (2025)
Invariant Labs showed that a malicious instruction placed in an issue on a public repository could be read by an agent connected through the GitHub MCP server.
What happened
- The agent then accessed the user's private repositories and could leak details such as private repository names and personal information.GitHub MCP Exploited: Accessing private repositories via MCP
- Recommended mitigations include giving agents access only to the repositories they need and monitoring agent tool calls.GitHub MCP Exploited: Accessing private repositories via MCP
The failure pattern
Watch the pattern: Indirect prompt injection changes agent behavior
Safeguards that address it
CollectSEA's engineering analysis of what would have prevented or contained this failure.
- Scope agent credentials per task and repositoryGrant tokens only for the repositories the current task needs so injected instructions cannot reach private data.
- Separate untrusted content from instructions and review tool callsTreat issue text as data, and require confirmation before an agent reads from one trust domain and writes to another.
Related standards
CollectSEA's mapping through this incident's failure pattern; not an official determination by the standards bodies.
- ASI01 Agent Goal Hijack
- ASI02 Tool Misuse and Exploitation
- ASI03 Identity and Privilege Abuse
- ASI06 Memory and Context Poisoning
- ASI10 Rogue Agents
- LLM01 Prompt Injection
- LLM02 Sensitive Information Disclosure
- LLM03 Excessive Agency
- LLM10 Improper Output Handling
- AC-3 Access Enforcement
- AC-4 Information Flow Enforcement
- AC-5 Separation of Duties
- AC-6 Least Privilege
- SI-10 Information Input Validation
- RV.3.4 Update the development process
- MAP 5.1 Estimate impacts from past uses and public incident reports
- Goal 3 Reducing entire classes of vulnerability
- CWE-862 Missing Authorization
- CWE-1427 Improper Neutralization of Input Used for LLM Prompting
- CWE-250 Execution with Unnecessary Privileges
Building something similar?
Describe your design and see every precedent that applies, with safeguards you can hand to your coding agent.
Incidents with the same pattern
Prompt injection makes GitHub Copilot turn off its own confirmations and run commands (CVE-2025-53773)
Instructions planted in content the agent reads could make GitHub Copilot write "chat.tools.autoApprove": true into the project's .vscode/settings.json, which turns off all user confirmations.
Prompt injection in a README plus weak allow-list matching lets Gemini CLI silently run attacker commands (2025)
Researchers hid a prompt injection inside a README.md (in the text of a software license) so that Gemini CLI, asked only to inspect a codebase, would request shell commands.
Hidden instructions in a support ticket make an MCP-connected assistant expose private SQL tables (Supabase MCP, 2025)
General Analysis showed that hidden instructions in a customer support ticket could make a developer's MCP-connected assistant query a private table of integration tokens.
EchoLeak: zero-click prompt injection lets a crafted email exfiltrate Microsoft 365 Copilot data (2025)
EchoLeak (CVE-2025-32711, CVSS 9.3) is a zero-click vulnerability in Microsoft 365 Copilot in which a crafted email could trigger indirect prompt injection.
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