CVE-2026-70306
Summary
by MITRE • 08/11/2026
Improper neutralization of input during web page generation ('cross-site scripting') in Microsoft Office SharePoint allows an unauthorized attacker to perform spoofing over a network.
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Analysis
by VulDB Data Team • 08/11/2026
Cross-site scripting vulnerabilities in Microsoft Office SharePoint represent a critical security flaw that enables unauthorized attackers to inject malicious scripts into web pages viewed by other users. This particular vulnerability stems from insufficient input validation and sanitization during the web page generation process, allowing attackers to embed malicious code that executes in the context of the victim's browser session. The weakness specifically manifests when SharePoint applications fail to properly neutralize user-supplied data before incorporating it into dynamically generated web content, creating an environment where attacker-controlled inputs can be interpreted as executable code rather than benign text.
The technical exploitation of this vulnerability occurs through the manipulation of input parameters that are subsequently rendered in web pages without adequate sanitization. Attackers can craft malicious payloads that leverage the SharePoint application's dynamic page generation capabilities to inject JavaScript or other client-side code into web documents. When legitimate users browse these compromised pages, their browsers execute the embedded scripts, potentially leading to session hijacking, credential theft, or unauthorized actions performed on behalf of the victim. This type of vulnerability directly maps to CWE-79 - Improper Neutralization of Input During Web Page Generation, which is classified as a fundamental weakness in web application security. The ATT&CK framework categorizes this under T1566 - Phishing and T1059 - Command and Scripting Interpreter, highlighting the attack vectors and execution methods available to threat actors.
The operational impact of this vulnerability extends beyond simple data theft, as it enables sophisticated social engineering campaigns that can compromise entire user sessions. Attackers can leverage the persistent nature of XSS vulnerabilities to establish backdoors, harvest authentication tokens, or redirect users to malicious sites that appear legitimate. The SharePoint environment particularly amplifies these risks due to its typical role in corporate environments where users trust internal applications and may have elevated privileges within the organization. Furthermore, the cross-site scripting attack vector allows for the exploitation of trust relationships between users and SharePoint servers, potentially enabling lateral movement within networks where SharePoint serves as a central collaboration platform.
Effective mitigation strategies must address both the immediate vulnerability and underlying architectural weaknesses in input handling processes. Organizations should implement comprehensive input validation frameworks that sanitize all user-supplied data before processing, employ Content Security Policies to restrict script execution, and utilize proper output encoding techniques during web page generation. The implementation of web application firewalls specifically configured to detect and block XSS attack patterns provides an additional layer of defense. Regular security assessments and penetration testing should target input validation mechanisms to identify potential injection points that could be exploited in similar fashion. Microsoft recommends applying the latest security updates and patches as soon as they become available, while also implementing proper access controls and user education programs to reduce the overall risk surface. The vulnerability underscores the critical importance of defense-in-depth strategies that combine multiple security controls rather than relying on any single mitigation technique.