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Researchers have discovered EchoLeak, a zero-click vulnerability in Microsoft 365 Copilot that allows attackers to exfiltrate sensitive data without user interaction. The exploit leverages prompt injection via crafted emails, causing Copilot to leak internal information through malicious markdown links. Mitigation strategies include prompt isolation, input sanitization, disabling auto-rendering of untrusted content, restricting context access, monitoring AI output, and user awareness training.
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Microsoft disclosed **CVE-2025-32711**, a critical information disclosure flaw in **Microsoft 365 Copilot** that researchers later detailed as **EchoLeak**, describing it as the first reported real-world **zero-click prompt injection** exploit in a production LLM system. The vulnerability carried a **CVSS 9.3** rating and allowed a remote, unauthenticated attacker to exfiltrate sensitive data over the network without user interaction, reportedly by sending a single crafted email that Copilot would process. Research describing the exploit said the attack chained multiple bypasses across LLM trust boundaries, including evasion of Microsoft’s XPIA classifier, use of reference-style Markdown to bypass link redaction, auto-fetched images, and abuse of a Microsoft Teams proxy allowed by content security policy to extract data. Microsoft said the issue had already been fully mitigated in the cloud service and required no customer action, while the broader research and follow-on reporting framed the incident as evidence that prompt injection and "AIjacking" can enable full data exfiltration in enterprise copilots unless controls such as prompt partitioning, stronger filtering, provenance-based access control, stricter CSPs, least privilege, and continuous adversarial testing are in place.
Jun 29, 2026
Varonis Threat Labs disclosed **SearchLeak**, a critical exploit chain in Microsoft 365 Copilot Enterprise Search that could let an attacker steal sensitive enterprise data after a user clicked a single trusted `microsoft.com` link. Microsoft tracked the issue as **`CVE-2026-42824`** and remediated it on the backend. According to the researchers, the attack could expose data available through the victim’s Microsoft Graph permissions, including emails, calendar entries, meeting notes, SharePoint content, OneDrive files, and potentially MFA-related messages, though no in-the-wild exploitation was reported. The technique chained three weaknesses: **parameter-to-prompt injection** through the Copilot Search `q` parameter, an **HTML streaming race condition** that allowed an injected image tag to render before sanitization, and abuse of a **Bing allowlist** in Content Security Policy to exfiltrate the retrieved data through Bing’s server-side image fetch behavior. Researchers said the attack required no plugins, elevated privileges, or second user interaction, highlighting how AI prompt injection can revive older web security flaws in enterprise platforms. Microsoft rated the flaw critical, while public severity scoring differed across sources, and defenders were advised to watch for suspicious Copilot Search URLs containing encoded or HTML payloads and unusual Bing image endpoint traffic.
Jun 29, 2026
Researchers reported that vulnerabilities in Microsoft 365 Copilot and Consumer Copilot allowed attackers to turn prompt injection into data exfiltration, memory poisoning, and persistent compromise. Microsoft assigned `CVE-2026-24299` to the main issue set and rolled out fixes across late 2025 and early 2026, while a related Microsoft Excel flaw, `CVE-2026-26144`, showed how a conventional application bug could be chained with Copilot Agent mode to silently extract spreadsheet data. In the Copilot attacks, malicious content abused HTML preview rendering to leak sensitive information through external requests, first with CSS background images and later with `@font-face`, and researchers said users could be coerced into triggering the preview during normal interaction, creating a near zero-click exfiltration path. The research also showed that Copilot’s memory features could be poisoned to add or delete stored facts and implant persistent instructions that altered future sessions, enabling a backdoor dubbed **SpAIware** that continued leaking secrets over time. Similar issues were described in consumer Copilot, including durable-memory manipulation and browser-navigation exfiltration through Edge-integrated tooling. The findings underscore a broader security shift: AI assistants can collapse trust boundaries inside host applications, raising the impact of older flaws and forcing defenders to reassess assistant permissions, restrict outbound network access from AI-enabled apps, and separately monitor AI-initiated network activity.
Jun 29, 2026