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SearchLeak: How We Turned M365 Copilot Into a One-Click Data Exfiltration Weapon
Discovery of 'SearchLeak', a three-stage vulnerability chain in Microsoft 365 Copilot Enterprise that enables silent data exfiltration.
TL;DR
Researchers have identified a critical vulnerability chain called SearchLeak that allows attackers to exfiltrate enterprise data via Microsoft 365 Copilot. By combining prompt injection with an HTML race condition and Bing-based SSRF, attackers can bypass security controls with a single click.
The 'SearchLeak' vulnerability represents a sophisticated multi-stage attack chain targeting Microsoft 365 Copilot Enterprise. The process begins with Parameter-to-Prompt (P2P) injection, where an attacker crafts a URL containing a malicious 'q' parameter that instructs the AI to search for sensitive information and embed it within an HTML image tag. During the streaming phase of the AI's response, a race condition occurs: the browser renders the <img> tag before the platform's security sanitizer can wrap the output in protective <code> blocks. To bypass the Content Security Policy (CSP) that prevents direct requests to attacker-controlled domains, the exploit leverages a Server-Side Request Forging (SSRF) vulnerability in Bing's 'Search by Image' feature. By pointing the image source to a Bing endpoint, the attacker forces Bing's backend to fetch the data from the attacker's server, effectively using Bing as an exfiltration proxy. This allows for the silent theft of emails, security codes, and organizational documents without requiring any special permissions or user interaction beyond clicking a trusted Microsoft link. Microsoft has since patched this vulnerability under CVE-2026-42824.