- EchoLeak allowed, for the first time, to exfiltrate data from Copilot no user interaction.
- The attack relied on the hidden injection of instructions into seemingly legitimate emails.
- Microsoft has fixed the breach at the server level, and there is no evidence of active exploitation.
La Artificial Intelligence is revolutionizing business productivity, but it also brings with it unprecedented challenges in terms of ciberseguridad. Microsoft 365 Copilot, the popular assistant powered by large language models (LLM), has recently made headlines across the industry for a serious security breach dubbed EchoLeakWhat makes this vulnerability so special and dangerous? Why has it set off alarm bells in the field of data protection and information management? IA in companies?
In this article we will thoroughly analyze the EchoLeak case.: how such a vulnerability in Copilot emerged, what exactly the zero-click attack was, why it has such serious implications for corporate AI security, and most importantly, what are the best strategies and measures to prevent this kind of incident from happening again in the future. If you're interested in knowing what happened to security in Microsoft Copilot and how to protect yourself against similar threats, join us on this comprehensive tour.
EchoLeak: A New Era in Artificial Intelligence Vulnerabilities
Vulnerability EchoLeak, identified and named by the firm Aim Security, marks a before and after in the world of cybersecurity. It is the First zero-click breach in an AI agent intended for business environments, capable of exfiltrating confidential information without the victim having to interact at all. Unlike traditional phishing attacks or malware, no clicks are needed here, downloads nor compromised credentials: the mere regular use of Copilot by the user may be enough for the data to fall into the wrong hands.
EchoLeak was classified as a critical vulnerability (CVE-2025-32711) and registered with international security systems. Microsoft acted swiftly, patching the server-side flaw in May 2025, shortly after receiving the researchers' report. To date, it has not been actively exploited in real-world environments, but its conceptual and technical impact is enormous: it demonstrates how AI models themselves can become a nearly invisible and fully automatable attack vector.
What is Microsoft 365 Copilot and why is it affected?
Microsoft 365 Copilot is the intelligent assistant built into the Microsoft 365 office suite. Works in applications like Become, Excel, Outlook, and Teams, helping you compose emails, analyze data, organize information, and answer questions about all types of business documents. On a technical level, it combines advanced language models (such as those of OpenAI) with Microsoft Graph, the system that connects and maps your organization’s data: files, emails, chats, and more.
The heart of Copilot is its RAG capability (Retrieval Augmented Generation), a process that allows you access and retrieve relevant information in real time from all available sources to compose more accurate, useful, and personalized responses. This means Copilot can draw conclusions and generate text using both the public data it was trained on and sensitive and private information stored in the company's environment.
This is precisely where the power and the risk of Copilot lie.: Automatic cross-platform access to internal data allows AI to be very effective, but it also expands the attack surface if appropriate filters and controls are not applied in the retrieval and response generation process.
How was the EchoLeak vulnerability exploited in Copilot?
El EchoLeak's modus operandi It was as simple as it was ingenious and dangerous. The attack began with the victim being sent a seemingly harmless email, well written and with all the appearance of an ordinary business communication. Where was the catch? In that this message contained a hidden instruction intended to deceive Copilot using a technique known as prompt injection.
This disguised text went undetected by conventional defenses and automated classifiers that typically detect manipulation, such as Microsoft's XPIA (Cross-Prompt Injection Attack) filter. Because it was written naturally and contextually, Copilot's AI incorporated it into its context memory whenever the user performed a related query, for example, requesting a summary of recent reports or an extract of key data for a project.
Once in the context, the hidden injection instructed Copilot to gather sensitive information (emails, internal files, Teams or OneDrive data, chat history, etc.) and, in its response, embedded that sensitive data in a URL or a special image. By automatically loading the response generated by Copilot, the browser could end up sending the leaked information directly to a server under the attacker's control, without either the user or monitoring systems noticing anything unusual.
No step required any interaction from the victim.The entire cycle—from sending the message to the data leak—could happen in the background, silently and almost untraceably, following the usual workflow in the Microsoft 365 suite.
Repercussions and implications of the zero-click attack
What cybersecurity teams are most concerned about about EchoLeak is its automatable nature and the possibility of scaling the attack to one or more targets within a single company. By not relying on classic human errors—such as opening dangerous attachments or following malicious links—the attack can bypass many traditional prevention barriers.
Furthermore, The vulnerability did not depend on a single flaw, but on the combination of several weaknesses in the design of Copilot and its integration with information retrieval systems (IRS). Aim Security experts detail that, to successfully exploit EchoLeak, it was necessary to evade several layers of protection: cross-prompt injection attacks, external link blocks, and content security policies (CSPs). Even so, they managed to exfiltrate data through URLs that the organization itself considered safe, such as those of Teams or SharePoint, complicating the detection and blocking of malicious traffic.
EchoLeak is the perfect example of that The massive integration of AI into the work environment multiplies the exposure surfacesWhen an automated agent has access to emails, documents, and conversations, any vulnerability can have devastating consequences, especially for businesses and industries that handle sensitive information.
What data was exposed by EchoLeak?
The information potentially compromised by the vulnerability was very wideDepending on Copilot's permissions and the scope of the organization, the attack allowed access to:
- Emails received and sent
- Documents stored in OneDrive, SharePoint and internal folders
- Teams chats and messages
- Conversation histories and contexts in Copilot
- Contextual data linked to the user or organizational group
In practice, Any information Copilot had access to could be exfiltrated. If the vulnerability was successfully exploited, the seriousness of EchoLeak lies in its evidence of how an automated assistant can become the best backdoor an attacker could dream of.
Why was it so difficult to detect and protect?
The characteristics that make EchoLeak particularly dangerous also make it difficult to detect and block. Some of these characteristics include:
- No human interaction required: “Zero-click” attack models eliminate the usual weakest link—the user.
- Use valid channels and permissions: Takes advantage of internal permissions and trusted URLs.
- Camouflaged writing: Prompt injections are structured like natural text, evading automatic filters and classifiers.
- Silent exfiltration: Data is extracted using resources embedded in responses, such as images or links, which the browser loads invisibly to the user.
The sophistication of this attack underscores that Traditional defenses are no longer sufficient against AI-based threats.New detection and protection models need to be developed that understand the inner workings of LLM systems, the context in which they operate, and the information flows they generate.
Microsoft and community response to EchoLeak
Microsoft reacted quickly as soon as it was notified of the vulnerability. The company Fixed the bug during May 2025 at the server level, so users didn't need to perform any manual actions or install additional updates. Furthermore, Microsoft publicly confirmed that there was no evidence of active exploitation prior to the mitigation.
The tech giant thanked Aim Security for the responsible disclosure of the problem, and assured that it is implementing additional defense-in-depth measures to prevent similar incidents in the future. The cybersecurity community itself, including Forrester and other analysts, has agreed that the swift action has been exemplary, although they warn that EchoLeak is just the tip of the iceberg of a much larger security problem in AI agents..
Among the actions taken and recommendations circulating in the sector, the following stand out:
- Continuous review of request injection filters on AI-powered platforms.
- Granular control of permissions and input scope: limit data exposure to only what is strictly necessary.
- Post-processing filtering to block generated responses that include external links or suspicious structures.
- Precise configuration of RAG engines to exclude unverified external sources, especially external emails.
- Audit and monitoring of permits in connected apps like Teams and SharePoint.
Companies must rethink their defense and surveillance models every time they introduce conversational agents or generative models into their workflows. The speed with which AI evolves demands an equally agile and innovative response in cybersecurity.
Could it happen again? The future of AI security
Both Copilot's creators and independent experts agree: EchoLeak is just the first serious warning of new vulnerabilities linked to artificial intelligence.The pace of adoption of language model-based solutions—both in Microsoft 365 and other major platforms—makes it inevitable that new breaches will be discovered if controls and protection strategies are not strengthened.
The EchoLeak case illustrates a new paradigm: the appearance of “scope violations” in LLMs, where AI can extract and display information that should never have left a private context, without the users' intention or knowledge.
Organizations that rely on AI assistants must therefore strengthen their update policies, permanently audit permissions and information retrieval models, and stay abreast of new attack techniques, especially regarding prompt injection and the combined use of legitimate channels for covert data exfiltration.
The integration of artificial intelligence into the corporate environment is unstoppable, but it cannot be separated from a decisive investment in security and training.EchoLeak is a warning, but also an opportunity to anticipate and secure systems before even more sophisticated threats emerge.
In closing, it can be said that the EchoLeak vulnerability marked a turning point in risk management associated with enterprise artificial intelligence. Its discovery and rapid remediation prevented damage, demonstrating the importance of constantly updating protection and surveillance strategies in a rapidly evolving threat landscape.
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