FHN 
Microsoft has disclosed three high-severity information disclosure vulnerabilities affecting Microsoft 365 Copilot and Copilot Chat in Microsoft Edge. These flaws could allow attackers to bypass logical security boundaries and access sensitive enterprise data handled by the AI system.
All three vulnerabilities carry a CVSS score of 7.5, indicating a high impact on data confidentiality. The issues can be exploited remotely with low complexity and do not require prior privileges or user interaction.
As AI assistants become tightly integrated into enterprise environments, these types of vulnerabilities increase the risk of unintended data exposure across emails, documents, and internal communications.
Technical Breakdown of the Vulnerabilities
The vulnerabilities originate from improper input and output handling within the AI processing pipeline. Attackers can exploit these weaknesses using prompt injection techniques, where specially crafted inputs manipulate the model’s behavior.
The identified vulnerabilities include:
- CVE-2026-26129 – Improper neutralization of special elements (CWE-138), allowing manipulation of how Copilot parses structured input
- CVE-2026-26164 – Injection vulnerability (CWE-74) affecting downstream components, potentially causing unintended data disclosure
- CVE-2026-33111 – Command injection flaw (CWE-77) in Copilot Chat within Microsoft Edge, enabling execution of unauthorized commands
These vulnerabilities primarily impact confidentiality, with no direct effect on system integrity or availability.
Enterprise Risk and Attack Impact
Because Microsoft 365 Copilot has deep access to enterprise data sources such as emails, Teams conversations, Word documents, and SharePoint files, exploitation could act as a silent data exfiltration channel.
By submitting carefully crafted prompts, an attacker could:
- Extract sensitive financial or operational data
- Access internal communications and documents
- Retrieve personally identifiable employee information
This type of attack leverages the AI model’s context awareness, making it difficult to detect through traditional security controls.
The vulnerabilities have been addressed by Microsoft at the service level. Since Copilot operates as a cloud-managed platform, security patches and input validation improvements were deployed centrally without requiring user action.
Organizations using Microsoft 365 Copilot and Copilot Chat in Edge are automatically protected, highlighting the advantage of centralized patch management in cloud-based AI services.
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