CVE-2025-52486: DNN (DotNetNuke) XSS Vulnerability

CVE-2025-52486 Overview

CVE-2025-52486 is a reflected cross-site scripting (XSS) vulnerability in DNN Platform, formerly known as DotNetNuke. The flaw affects versions 6.0.0 through versions before 10.0.1. Specially crafted content in URLs can be processed by the TokenReplace mechanism without proper sanitization by certain SkinObjects. Attackers can inject script content that executes in a victim's browser when the malicious URL is visited. The DNN maintainers released a fix in version 10.0.1. The weakness is classified as [CWE-79], improper neutralization of input during web page generation.

Critical Impact
Unauthenticated attackers can craft URLs that execute arbitrary JavaScript in the context of the targeted DNN site, enabling session theft, credential harvesting, and content manipulation.

Affected Products

DNN Platform (DotNetNuke) versions 6.0.0 to before 10.0.1
DNN.PLATFORM component using TokenReplace with vulnerable SkinObjects
Websites and CMS deployments built on affected DNN releases

Discovery Timeline

2025-06-21 - CVE-2025-52486 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-52486

Vulnerability Analysis

DNN Platform provides a token replacement engine that expands [Object:Property] style tokens into dynamic content rendered by skin objects. Certain skin objects pass URL-derived data through TokenReplace without applying output encoding suitable for the destination context. An attacker who supplies specially crafted values in URL parameters can cause the rendered page to include attacker-controlled markup. The reflected content executes as JavaScript in the browser of any user who loads the crafted URL. Exploitation requires user interaction, typically clicking a prepared link, but no authentication is required.

Root Cause

The root cause is missing context-aware output encoding inside BaseCustomTokenReplace and dependent property accessors used by skin objects. Token values were emitted into HTML, JavaScript, CSS, and URL contexts using the same replacement path, so hostile input from a URL flowed unchanged to the response. The patch introduces new property access classes, including HtmlEncodingPropertyAccess, JavaScriptEncodingPropertyAccess, and UrlEncodingPropertyAccess, that apply encoding appropriate to each output context.

Attack Vector

Exploitation is network-based and unauthenticated. An attacker crafts a URL targeting a DNN page that renders one of the vulnerable skin objects, embedding payload characters that break out of the intended token context. The victim clicks the link, the server reflects the payload, and the browser executes the injected script under the DNN site's origin.

text

// Patch excerpt: new encoding property accessors added to DotNetNuke.Library.csproj
<Compile Include="Services\Tokens\PropertyAccess\HtmlEncodingPropertyAccess.cs" />
<Compile Include="Services\Tokens\PropertyAccess\JavaScriptEncodingPropertyAccess.cs" />
<Compile Include="Services\Tokens\PropertyAccess\UrlEncodingPropertyAccess.cs" />

Source: GitHub Commit 74f6de6

csharp

// Patch excerpt: BaseCustomTokenReplace.cs unknown-object handling refactored
else if (this.DebugMessages)
{
    string message = Localization.GetString(
        "TokenReplaceUnknownObject",
        Localization.SharedResourceFile,
        this.FormatProvider.ToString());
    if (message == string.Empty)
    {
        message = "Error accessing [{0}:{1}], {0} is an unknown datasource";
    }

    result = string.Format(message, objectName, propertyName);
}

Source: GitHub Commit 74f6de6. The patch restricts reflection of unknown token object names to debug mode so attacker-supplied identifiers no longer echo back to production responses.

Detection Methods for CVE-2025-52486

Indicators of Compromise

Web server access logs showing URLs containing <script>, javascript:, onerror=, or encoded variants (%3Cscript%3E) in query strings targeting DNN pages
Requests to DNN URLs that include token-like patterns such as [User: or [Portal: combined with HTML metacharacters
Unexpected outbound requests from user browsers to attacker-controlled domains after visiting DNN pages

Detection Strategies

Inspect HTTP request logs for query parameters that decode into HTML, JavaScript, or event-handler syntax reaching DNN skin object endpoints
Compare deployed DNN Platform assemblies against the fixed 10.0.1 release to identify hosts still exposing the vulnerable TokenReplace code path
Use a web application firewall (WAF) in detection mode to flag reflected XSS payloads in requests and matching content in responses

Monitoring Recommendations

Alert on DNN responses that echo URL parameter values into HTML without encoding, using response body inspection or DAST scans
Monitor authentication and administrative activity for sessions that follow suspicious inbound referrers containing script payloads
Track browser Content Security Policy (CSP) violation reports from DNN sites to surface reflected injection attempts

How to Mitigate CVE-2025-52486

Immediate Actions Required

Upgrade DNN Platform to version 10.0.1 or later on all affected sites
Audit custom skin objects and modules that consume TokenReplace output for missing encoding
Rotate administrative credentials and invalidate active sessions if reflected XSS exploitation is suspected

Patch Information

The fix is delivered in DNN Platform 10.0.1. The maintainers added dedicated encoding property accessors (HtmlEncodingPropertyAccess, JavaScriptEncodingPropertyAccess, UrlEncodingPropertyAccess) and hardened BaseCustomTokenReplace so unknown token objects are no longer reflected outside debug mode. Details are available in the GitHub Security Advisory GHSA-pf4h-vrv6-cmvr and the remediation commit 74f6de6.

Workarounds

Deploy a WAF rule set that blocks reflected XSS patterns against DNN endpoints until the upgrade completes
Disable or replace custom skins and skin objects that render URL-derived tokens directly into HTML
Enforce a strict Content Security Policy (CSP) that disallows inline scripts and unknown external origins to reduce impact of script injection

bash

# Example nginx rule to block obvious reflected XSS payloads reaching DNN
if ($args ~* "(<|%3C)script|javascript:|onerror=|onload=") {
    return 403;
}