CVE-2026-42824 turns Microsoft 365 Copilot into a data exfiltration tool. Learn how the SearchLeak attack chain works and what defenders must do now.

Varonis disclosed SearchLeak (CVE-2026-42824), a max-severity Microsoft 365 Copilot flaw chaining a prompt injection with two web bugs so one click on a real microsoft.com link silently exfiltrated MFA codes, email, and files. Patched server-side.

A critical vulnerability chain in Microsoft 365 Copilot Enterprise that let attackers steal sensitive corporate data, MFA codes, email contents, calendar details, and confidential files with nothing more than a single click on a link pointing to a legitimate Microsoft domain. Dubbed SearchLeak, uncovered by Varonis Threat Labs and tracked as CVE-2026-42824 , the flaw earned Microsoft’s maximum severity rating before being patched. Its significance lies less in any single bug than in how it fuses a new AI-specific weakness with two well-worn web security flaws, turning Copilot Enterprise Search into a silent exfiltration channel. SearchLeak is not a single flaw; it is a chained exploit that weaponizes Microsoft 365 Copilot Enterprise Search as a silent data exfiltration engine. Detailed by Varonis researcher Dolev Taler, the attack combines three distinct weaknesses: a Parameter-to-Prompt (P2P) Injection, an HTML rendering race condition, and a Server-Side Request Forgery (SSRF) via Bing’s image search endpoint. Individually, each vulnerability is manageable. Chained together, they create a one-click attack capable of stealing virtually any data the victim can access within their Microsoft 365 tenant without requiring any special privileges, plugins, or secondary interactions. Microsoft 365 Copilot Vulnerability Chain Stage 1 — P2P Injection: Microsoft 365 Copilot Search accepts a q URL parameter intended for natural language search queries. The flaw is that whatever value is placed in the q parameter is interpreted by Copilot’s AI engine not just as a search string, but as executable instructions. An attacker crafts a malicious URL that points to a trusted microsoft.com domain and commands Copilot to search the victim’s mailbox and embed the extracted data in an image URL. Because the link resolves to a legitimate Microsoft domain, traditional anti-phishing and URL protection tools do not flag it. Stage 2 — Racing the Guardrail: Microsoft’s mitigation for dangerous AI-generated HTML is to wrap Copilot output in <code> blocks, preventing the browser from rendering it as markup. However, this wrapping only occurs after Copilot finishes its generation phase. During the streaming phase, raw HTML including attacker-injected <img> tags is temporarily rendered live in the DOM. The browser fires off the HTTP request before the sanitizer even activates, making this a textbook race condition bypass. Stage 3 — SSRF via Bing: The victim’s browser cannot directly contact an attacker-controlled server due to the Content Security Policy (CSP) on m365.cloud.microsoft . However, *.bing.com is CSP-allowlisted. Bing’s “Search by Image” feature accepts a imgurl parameter and performs a server-side fetch of the provided URL to analyze it. The attacker embeds the stolen data directly in the path of this Bing image-search URL. Bing’s backend unwittingly relays the stolen data to the attacker’s server, bypassing the CSP entirely. Microsoft 365 Copilot Attack Chain (Source: Varonis Threat Labs) The complete attack requires only a crafted link sent via email, Teams, Slack, or any messaging channel. When clicked, Copilot silently searches the victim’s mailbox, generates a response with embedded stolen data in a Bing image URL, and the attacker’s server logs the exfiltrated information all in seconds, with no second click. Defense Recommendations Microsoft has fully patched the SearchLeak server-side; no user action is required to receive the fix. However, Varonis recommends security teams: Monitor Copilot Search URLs for encoded payloads in the q parameter containing HTML or image-embedding instructions Audit CSP allowlists for any domain that performs server-side fetches on user-supplied URLs Treat AI streaming output as untrusted sanitization must occur at render time, not as a post-processing step Alert users to inspect Microsoft 365 links with long, encoded query strings before clicking SearchLeak follows Varonis’ earlier discovery of Reprompt , a similar one-click data exfiltration chain affecting Copilot Personal. Together, these findings underscore how AI assistants are creating new, hard-to-detect attack surfaces by reactivating previously unexploitable classic vulnerabilities in new contexts. Follow us on  Google News ,  LinkedIn , and  X  to Get More Instant Updates. The post Critical Microsoft 365 Copilot Vulnerability Allows Attackers to Steal Data in One Click appeared first on Cyber Security News .

Ab sofort können Unternehmen autonome KI-Agenten in ihrer Arbeitsumgebung einsetzen – doch der Start wird von Sicherheitslücken und Governance-Problemen überschattet.Neues Preismodell: Zwei Stufen für den KI-EinsatzMicrosoft hat am 17. Juni 2026 den globalen Rollout von Copilot Cowork gestartet. Das System kombiniert die bestehende monatliche Lizenz – 30 Euro pro Nutzer für Unternehmen, 20 Euro für […] The post SearchLeak (CVE-2026-42824): Kritische Lücke in Microsoft 365 Copilot appeared first on BornCity.

Eine kritische Schwachstelle in Microsofts KI-Assistenten Copilot für Microsoft 365 hätte Angreifern den Zugriff auf vertrauliche Daten ermöglichen können – und das mit nur einem einzigen Klick.Die „SearchLeak“-Lücke im DetailDie als CVE-2026-42824 registrierte Sicherheitslücke mit dem Codenamen „SearchLeak“ wurde Mitte Juni 2026 von Forschern der Sicherheitsfirma Varonis aufgedeckt. Sie basiert auf einer komplexen dreistufigen Angriffskette, […] The post Copilot-Lücke SearchLeak: Microsoft schließt kritische Sicherheitslücke appeared first on BornCity.

Der Tech-Riese kämpft gleich an zwei Fronten: Eine kritische Sicherheitslücke in Copilot und eine milliardenschwere Aktionärsklage setzen den Konzern unter Druck. Sicherheitspanne: Ein Klick genügte für den Datenklau Sicherheitsforscher von Varonis Threat Labs haben eine schwerwiegende Schwachstelle in Microsoft 365 Copilot Enterprise aufgedeckt. Die als CVE-2026-42824 registrierte Lücke – von den Experten auf den Namen […] The post Copilot SearchLeak: Kritische Lücke ermöglichte Datenklau mit einem Klick appeared first on BornCity.

Varonis Threat Labs uncovered SearchLeak, a one-click attack chain against Microsoft 365 Copilot Enterprise Search that could exfiltrate emails, calendar details, and indexed files through a trusted microsoft.com link. Microsoft assigned CVE-2026-42824 and mitigated the issue on the backend, while defenders are advised to monitor suspicious q-parameter payloads and unusual Bing...

Varonis Threat Labs discovered SearchLeak, a three-stage attack chain that turns Microsoft 365 Copilot Enterprise Search into a silent data exfiltration path by combining P2P injection, an HTML rendering race condition, and Bing-based SSRF. Microsoft patched the issue as CVE-2026-42824 with critical severity, and the chain could expose emails, security codes,...

A critical vulnerability chain called SearchLeak in Microsoft 365 Copilot Enterprise could let attackers steal sensitive data from mailboxes, OneDrive, and SharePoint through a specially crafted URL. Microsoft fixed the flaw as CVE-2026-42824, while researchers showed how prompt injection, an HTML rendering race condition, and a Bing SSRF issue could be chained to exfiltrate emails, calendar details, and documents. #Microsoft365CopilotEnterprise #SearchLeak #CVE-2026-42824 #Bing #Varonis

Microsoft patched the critical 'SearchLeak' vulnerability (CVE-2026-42824) in Copilot with server-side updates.

Introduction: The integration of Large Language Models (LLMs) into enterprise productivity suites has ushered in a new era of efficiency, but it has also introduced a novel attack surface that traditional security controls are ill-equipped to handle. The recent disclosure of CVE-2026-42824, dubbed "SearchLeak," in Microsoft 365 Copilot Enterprise Search serves as a critical wake-up call for organizations worldwide. This vulnerability demonstrated that a single click on a seemingly legitimate Microsoft domain link could allow attackers to silently exfiltrate emails, calendar data, MFA codes, and indexed files without any further user interaction, exposing the fundamental truth that an AI is only as secure as the data it is permitted to access.

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L'équipe de chercheurs en cybersécurité Varonis Threat Labs a découvert une vulnérabilité critique dans Microsoft 365 Copilot Enterprise, référencée sous le numéro CVE-2026-42824 et baptisée « SearchLeak », qui permettait aux pirates de dérober des données d'entreprise sensibles en un seul clic. Cette chaîne d'exploitation cible Copilot Enterprise Search en combinant une injection de prompts d'intelligence artificielle (IA), une condition de concurrence lors du rendu HTML et une falsification de...

2026年6月15日に公開された記事によると、Varonis Threat Labs がMicrosoft 365 Copilot Enterprise の脆弱性チェーン「SearchLeak」を発見したという。この脆弱性はCVE-2026-42824 として管理され、Microsoft

SearchLeak：Microsoft 365 Copilotのワンクリック脆弱性により機微なデータの窃取が可能に（CVE-2026-42824）

SearchLeak vulnerability in Microsoft 365 Copilot Enterprise enabled data theft via a crafted URL before Microsoft patched CVE-2026-42824.