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Microsoft 365 Copilot Flaw 'SearchLeak' Enabled One-Click Data Theft, Now Patched

June 17, 2026 at 09:52 EDT

Security
AI Agents
Sales & Business

Varonis Threat Labs has disclosed SearchLeak (CVE-2026-42824), a vulnerability chain in Microsoft 365 Copilot Enterprise Search that could leak a victim's emails, files and calendar data externally through a single click on a trusted Microsoft-domain link. Microsoft has already fixed the issue on the backend and says no customer action is required.

June 15, 2026 · Varonis Threat Labs

SearchLeak: One Click Could Drain a Copilot Inbox

A vulnerability chain (CVE-2026-42824) in Microsoft 365 Copilot Enterprise Search let a single click on a trusted microsoft.com link exfiltrate a victim's emails, files, calendar — even MFA codes. Microsoft has patched it on the backend; no user action required.

click — no password, no extra steps

CRITICAL

severity rated for CVE-2026-42824

known real-world exploits

The Attack Chain

STEP 1 · P2P

Parameter-to-Prompt

URL q param read as an executable prompt, not a search term

→

STEP 2 · RACE

<img> render

Browser fetches the image before the sanitizer can wrap it in a code block

→

STEP 3 · SSRF

CSP bypass

Routed via an allowlisted *.bing.com endpoint to attacker's server

Data Within Reach of the Prompt

✉ Email bodies & subjects 📁 SharePoint / OneDrive files 📅 Calendar details 🔑 MFA / OTP codes

Copilot reaches all of this through the user's Microsoft Graph permissions — its convenience became the attack surface.

Why filters fail

The link sits on a legitimate microsoft.com domain — conventional URL-filtering phishing defenses offer limited help.

Lessons going forward

Stronger data governance
Review CSP allowlists
Rethink when AI streaming output is sanitized

A familiar pattern: prompt injection + classic web flaw. It echoes the earlier "Reprompt" finding against Copilot Personal and the zero-click "EchoLeak" (CVE-2025-32711) — yet the same path still worked despite the Enterprise edition's added guardrails.

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