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CVE-2025-53787: Microsoft 365 Copilot BizChat Information Disclosure Vulnerability

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Overview

The Common Vulnerabilities and Exposures system has identified a high severity vulnerability, CVE-2025-53787, in Microsoft 365’s Copilot BizChat. This vulnerability poses a significant threat to users of this popular business communication tool, enabling potential system compromise or data leakage. Its severity underscores the critical need for organizations to prioritize cybersecurity in their operations, particularly when relying on widely used software applications like Microsoft 365.

Vulnerability Summary

CVE ID: CVE-2025-53787
Severity: High (8.2 CVSS Score)
Attack Vector: Network
Privileges Required: None
User Interaction: Required
Impact: Potential system compromise or data leakage

Affected Products

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Product | Affected Versions

Microsoft 365 | All versions prior to security update

How the Exploit Works

The vulnerability is a result of improper handling of user data within the Copilot BizChat application. An attacker can exploit this vulnerability by sending specially crafted messages or requests to a targeted user. Once the malicious content is interacted with, it triggers a flaw in the application’s security protocols, leading to unauthorized access to sensitive information.

Conceptual Example Code

This is a conceptual example of how the vulnerability might be exploited. In this instance, a malicious HTTP request is sent to the vulnerable endpoint:

POST /bizchat/v1/message HTTP/1.1
Host: target.example.com
Content-Type: application/json
{ "message_content": "<script>malicious_code_here</script>" }

Upon interaction with the malicious message, the attacker’s code is executed, potentially leading to unauthorized information disclosure, system compromise, or other unforeseen consequences.

Mitigation and Prevention

It is highly recommended that users of Microsoft 365’s Copilot BizChat apply the vendor’s security patch as soon as possible. This patch addresses the identified vulnerability and restores the application’s security integrity. If the patch cannot be applied immediately, using a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can serve as a temporary mitigation method. These tools can help detect and block malicious traffic aimed at exploiting this vulnerability.
However, while these temporary measures can provide some level of protection, they are not a substitute for applying the security patch, which provides the most comprehensive solution to this vulnerability. Regular software updates and patches remain a crucial part of an effective cybersecurity strategy.

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Disclaimer:

The information and code presented in this article are provided for educational and defensive cybersecurity purposes only. Any conceptual or pseudocode examples are simplified representations intended to raise awareness and promote secure development and system configuration practices.

Do not use this information to attempt unauthorized access or exploit vulnerabilities on systems that you do not own or have explicit permission to test.

Ameeba and its authors do not endorse or condone malicious behavior and are not responsible for misuse of the content. Always follow ethical hacking guidelines, responsible disclosure practices, and local laws.

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