CVE-2026-48562 Overview
CVE-2026-48562 is a cross-site scripting (XSS) vulnerability in Microsoft Office SharePoint. The flaw stems from improper neutralization of user input during web page generation [CWE-79]. An authenticated attacker can inject malicious script content that executes in the context of another user's browser session, enabling spoofing attacks over a network.
Exploitation requires the attacker to hold low-level privileges on the target SharePoint instance and requires user interaction from the victim. The vulnerability impacts confidentiality and integrity but does not affect availability.
Critical Impact
An authorized attacker can inject script content into SharePoint pages to spoof trusted application elements and manipulate the victim's browser session.
Affected Products
- Microsoft Office SharePoint (refer to the Microsoft Security Update CVE-2026-48562 advisory for specific affected versions)
Discovery Timeline
- 2026-06-09 - CVE-2026-48562 published to NVD
- 2026-06-09 - Last updated in NVD database
Technical Details for CVE-2026-48562
Vulnerability Analysis
The vulnerability is a stored or reflected cross-site scripting flaw in Microsoft Office SharePoint. SharePoint fails to properly neutralize user-supplied input before embedding it in dynamically generated web pages. When a victim loads the affected page, the browser parses and executes the injected payload in the trust context of the SharePoint origin.
Because SharePoint serves as a central collaboration platform, injected scripts can read or manipulate content visible to the victim. Attackers can use the flaw to spoof user interface elements, mislead users into authorizing actions, or harvest session-bound data.
Root Cause
The root cause is improper output encoding when rendering attacker-controlled values within HTML responses. SharePoint does not consistently apply context-aware encoding to user input that is reflected into the DOM, allowing HTML and JavaScript tokens to break out of the intended data context.
Attack Vector
The attack is conducted over the network. An attacker with valid SharePoint credentials submits crafted input containing script payloads through a vulnerable input vector. When a privileged user opens the affected page, the payload executes in their browser. User interaction is required, which typically aligns with normal SharePoint browsing behavior.
No verified public proof-of-concept is available. See the Microsoft Security Update CVE-2026-48562 advisory for additional technical details.
Detection Methods for CVE-2026-48562
Indicators of Compromise
- SharePoint page responses containing unexpected <script> tags, javascript: URIs, or event handlers such as onerror= and onload= inside user-generated fields.
- Outbound browser requests from authenticated SharePoint sessions to attacker-controlled domains that correlate with viewing specific list items or pages.
- Anomalous edits or uploads from low-privilege accounts that introduce HTML markup into fields normally containing plain text.
Detection Strategies
- Inspect SharePoint Unified Logging Service (ULS) and IIS logs for POST requests containing encoded script fragments such as %3Cscript%3E or <script.
- Hunt for content in lists, libraries, and web parts that contains HTML or JavaScript tokens in fields that should hold plain text.
- Correlate user-agent activity where a victim's session loads pages authored or modified by a recently created or low-trust account.
Monitoring Recommendations
- Forward SharePoint IIS, ULS, and Microsoft 365 audit logs to a centralized analytics platform for query-driven hunting.
- Alert on outbound DNS or HTTP requests originating from SharePoint page loads to uncategorized or newly registered domains.
- Monitor administrative changes to web part galleries, custom scripts, and content types that could host injected payloads.
How to Mitigate CVE-2026-48562
Immediate Actions Required
- Apply the Microsoft security update referenced in the Microsoft Security Update CVE-2026-48562 advisory to all affected SharePoint servers.
- Review SharePoint site permissions and remove contribute or edit rights from accounts that do not require them.
- Audit recently modified list items, pages, and web parts for embedded HTML or script content and remove suspicious entries.
Patch Information
Microsoft has issued a security update for SharePoint addressing CVE-2026-48562. Administrators should consult the Microsoft Security Update CVE-2026-48562 advisory for specific build numbers and update packages corresponding to their SharePoint deployment.
Workarounds
- Disable custom script execution on SharePoint sites where business needs do not require it using the Set-SPOSite -DenyAddAndCustomizePages setting.
- Restrict contributor permissions on collaboration sites until the patch is deployed, limiting who can submit input that reaches vulnerable rendering paths.
- Deploy a Content Security Policy (CSP) at the reverse proxy or load balancer to reduce the impact of injected scripts.
# Configuration example: restrict custom scripting on a SharePoint Online site
Set-SPOSite -Identity https://contoso.sharepoint.com/sites/team \
-DenyAddAndCustomizePages 1
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
