CVE-2026-48560: Microsoft SharePoint XSS Vulnerability

CVE-2026-48560 Overview

CVE-2026-48560 is a cross-site scripting (XSS) vulnerability in Microsoft Office SharePoint. The flaw stems from improper neutralization of input during web page generation [CWE-502]. An authenticated attacker with low privileges can inject script content that executes in the context of other SharePoint users. Successful exploitation enables spoofing over a network, undermining the integrity of pages rendered to victims.

The vulnerability requires authentication but does not require user interaction. Microsoft has published guidance through its Security Response Center, and administrators should review the advisory to identify affected SharePoint builds in their environment.

Critical Impact
Authenticated attackers can inject scripts into SharePoint pages to spoof content and manipulate trust boundaries for other users on the network.

Affected Products

Microsoft Office SharePoint (specific builds listed in the Microsoft advisory)
SharePoint Server deployments exposed to authenticated internal users
SharePoint sites accessible to low-privileged collaborators

Discovery Timeline

2026-06-09 - CVE-2026-48560 published to NVD
2026-06-09 - Last updated in NVD database

Technical Details for CVE-2026-48560

Vulnerability Analysis

The vulnerability is a stored or reflected cross-site scripting issue within SharePoint's page generation logic. SharePoint fails to neutralize attacker-controlled input before rendering it in HTML output. When a victim loads the affected page, the injected payload executes in their browser session, carrying the trust of the SharePoint origin.

Because the attack vector is network-based and requires only low privileges, any user with permission to post content, edit list items, or contribute to a site can plant a payload. No user interaction is required beyond normal navigation by the victim. The Exploit Prediction Scoring System places this issue in the upper-middle range of likelihood, reflecting SharePoint's history as a frequently targeted enterprise platform.

Root Cause

The root cause is missing or incomplete output encoding in a SharePoint web component that reflects user-supplied data into HTML. Input that should be treated as text is instead interpreted as markup, allowing <script> tags or event-handler attributes to execute. The associated weakness reference (CWE-502) in the NVD record indicates a deserialization pathway may also contribute to how untrusted data reaches the rendering layer.

Attack Vector

An authenticated attacker submits crafted input through a SharePoint feature that stores or reflects content into a rendered page. When another user visits the page, the browser executes the attacker's JavaScript under the SharePoint domain. The attacker can then forge UI elements, capture form data, or initiate authenticated requests on the victim's behalf. The confidentiality and integrity impact is rated low, and availability is not affected. No verified public proof-of-concept code is available at this time, and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2026-48560

Indicators of Compromise

Unexpected <script>, javascript:, or on*= event-handler strings persisted in SharePoint list items, document metadata, or page content
Outbound requests from end-user browsers to attacker-controlled domains immediately after loading SharePoint pages
SharePoint audit log entries showing edits to shared pages or web parts by low-privileged accounts

Detection Strategies

Inspect SharePoint content databases and IIS logs for stored payloads containing HTML or JavaScript syntax in fields meant for plain text
Hunt for anomalous DOM modifications and cross-origin requests originating from SharePoint URLs in browser telemetry
Correlate authentication events with content-edit actions to flag low-privileged accounts modifying shared pages at unusual times

Monitoring Recommendations

Enable SharePoint audit logging for item creation, page edits, and web part changes
Forward IIS, SharePoint ULS, and endpoint browser telemetry to a centralized analytics platform such as Singularity Data Lake for cross-source correlation
Alert on Content Security Policy violation reports from SharePoint origins to surface injected script execution

How to Mitigate CVE-2026-48560

Immediate Actions Required

Apply the SharePoint security update referenced in the Microsoft CVE-2026-48560 Update Guide
Review and reduce contributor-level permissions on sensitive sites until patches are deployed
Audit recently modified pages, list items, and web parts for embedded script content

Patch Information

Microsoft has issued guidance through the Microsoft Security Response Center. Administrators should consult the Microsoft CVE-2026-48560 Update Guide to identify the correct cumulative update for their SharePoint version and apply it across all farm servers.

Workarounds

Enforce a strict Content Security Policy on SharePoint sites to limit inline script execution
Restrict permissions so only trusted authors can create or edit pages and web parts
Disable custom script support on sites that do not require it using Set-SPOSite -DenyAddAndCustomizePages 1

bash

# Configuration example
# Disable custom script execution on a SharePoint Online site
Set-SPOSite -Identity https://contoso.sharepoint.com/sites/example -DenyAddAndCustomizePages 1