CVE-2020-0656 in Dynamics 365 Field Service
Summary
by MITRE
A cross site scripting vulnerability exists when Microsoft Dynamics 365 (on-premises) does not properly sanitize a specially crafted web request to an affected Dynamics server, aka 'Microsoft Dynamics 365 (On-Premise) Cross Site Scripting Vulnerability'.
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Analysis
by VulDB Data Team • 11/15/2025
The vulnerability identified as CVE-2020-0656 represents a critical cross site scripting flaw within Microsoft Dynamics 365 on-premises deployments that poses significant security risks to enterprise environments. This vulnerability stems from insufficient input validation and sanitization mechanisms within the web application layer of the Dynamics 365 platform, specifically when processing specially crafted web requests. The flaw allows malicious actors to inject malicious scripts into web pages viewed by other users, creating a persistent threat vector that can compromise user sessions and access sensitive organizational data. The vulnerability affects organizations that have deployed Microsoft Dynamics 365 in on-premises configurations rather than cloud-based deployments, making it particularly concerning for enterprises maintaining legacy systems or those with strict data sovereignty requirements.
The technical exploitation of CVE-2020-0656 occurs when an attacker crafts a malicious web request that bypasses the application's input sanitization controls, allowing arbitrary script execution within the context of a victim's browser session. This weakness typically manifests through improper handling of user-supplied input in web forms, URL parameters, or HTTP headers that are processed by the Dynamics 365 server components. The vulnerability is classified under CWE-79 as Improper Neutralization of Input During Web Page Generation, which specifically addresses the failure to properly sanitize user input before incorporating it into web page content. Attackers can leverage this flaw to execute malicious scripts in the victim's browser context, potentially leading to session hijacking, data theft, or unauthorized administrative actions within the Dynamics 365 environment.
The operational impact of this vulnerability extends beyond simple script injection, as it can enable attackers to establish persistent access to enterprise systems and potentially escalate privileges within the Dynamics 365 environment. Organizations utilizing on-premises Dynamics 365 deployments face heightened risk due to the complexity of maintaining security patches in traditional enterprise environments where update cycles may be longer than cloud-based solutions. The vulnerability can result in unauthorized access to customer records, financial data, and business intelligence stored within the Dynamics 365 system, potentially leading to significant financial losses and regulatory compliance violations. Attackers may also use this vulnerability as a foothold for further attacks within the enterprise network, leveraging the compromised Dynamics 365 instance to pivot to other internal systems.
Mitigation strategies for CVE-2020-0656 should prioritize immediate implementation of Microsoft's security patches and updates, as well as network-level protections such as web application firewalls and input validation controls. Organizations should implement comprehensive monitoring of web application logs to detect suspicious request patterns that may indicate exploitation attempts. The ATT&CK framework categorizes this vulnerability under T1566 for Phishing and T1059 for Command and Scripting Interpreter, highlighting the need for defensive measures that address both initial compromise vectors and post-exploitation activities. Security teams should also conduct regular security assessments of their on-premises Dynamics 365 deployments to identify and remediate similar input validation weaknesses. Additionally, implementing proper access controls, regular security training for users, and maintaining up-to-date security configurations can significantly reduce the attack surface and potential impact of exploitation attempts.