Executive Summary
TechStoriess reviews LLM agent vulnerabilities including EchoLeak (CVE-2025-32711), zero-click Microsoft 365 Copilot exfiltration via hidden prompts in PowerPoint speaker notes, and CVE-2025-53773, GitHub Copilot RCE via payloads in source code.
What Happened
TechStoriess reviews recent high-impact LLM agent vulnerabilities, including CVE-2025-32711 (“EchoLeak”), a zero-click prompt injection issue in Microsoft 365 Copilot enabling data exfiltration via hidden prompts in PowerPoint speaker notes, and CVE-2025-53773, which allowed remote code execution through GitHub Copilot by embedding injection payloads in source code.[8] The article emphasizes that no single control can fully prevent prompt injection and notes that mainstream developer and productivity tools integrating agents and MCP-style tool calls can be abused to leak corporate and customer data, affecting SaaS, fintech, and SMB environments.[8]
Affected Products
- Microsoft 365 Copilot
- GitHub Copilot
Vulnerability / Attack Technique
Prompt injection in documents and code leading to exfiltration or RCE
Technical Mechanism
Hidden prompts in speaker notes or source code are processed by Copilot, causing data exfiltration or code execution.
AI Security Category
LLM01:2025 Prompt Injection
Part of the Prompt Injection topic.
Part of the MCP Security topic.
Relevant Frameworks
RealGround Analysis
No single control fully prevents prompt injection. RealGround analysis: combine input handling, least privilege and output controls.
Recommended Controls
- Apply Copilot security updates
- Limit assistant access to sensitive documents
- Layer controls rather than relying on one filter
Related RealGround Service
Secure AI Agent Build · or start with the free AI Agent Security Scanner.
Sources
TechStoriess: https://www.techstoriess.com/ai-agent-security-practices-2026-prompt-injection-mcp-risks-data-leaks/
Summary and analysis written by RealGround from the source above; last updated 2026-10-18.