CVE-2025-55175: Quick.cms XSS Vulnerability via sLangEdit

CVE-2025-55175 Overview

CVE-2025-55175 is a reflected Cross-Site Scripting (XSS) vulnerability in Opensolution Quick.CMS. The flaw exists in the administrator panel functionality and is triggered through the sLangEdit parameter. Attackers can craft a malicious URL that, when opened by an authenticated administrator, executes arbitrary JavaScript in the victim's browser context.

The vulnerability is classified under CWE-79 (Improper Neutralization of Input During Web Page Generation). Only Quick.CMS version 6.8 was tested and confirmed vulnerable. Other versions may also be affected because the vendor did not disclose the vulnerable version range.

Critical Impact
Successful exploitation lets an attacker execute JavaScript in an administrator's browser, enabling session theft, administrative action hijacking, and content manipulation within the CMS.

Affected Products

Opensolution Quick.CMS 6.8 (confirmed vulnerable)
Earlier and later Quick.CMS versions (not tested, may be vulnerable)
Deployments exposing the administrator panel over the network

Discovery Timeline

2025-08-28 - CVE-2025-55175 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-55175

Vulnerability Analysis

The vulnerability resides in the Quick.CMS administrator panel, which processes the sLangEdit parameter without adequate output encoding. When the parameter value is reflected back into the rendered HTML response, an attacker-supplied payload is interpreted as executable JavaScript by the browser.

Exploitation requires user interaction. An attacker must trick an authenticated administrator into visiting a crafted URL, for example via phishing or a malicious link on a third-party site. Once executed, the injected script runs with the privileges of the administrator's browser session on the Quick.CMS origin.

Because the affected functionality is the admin panel, an attacker who lands JavaScript execution can invoke authenticated actions on behalf of the administrator. Typical consequences include exfiltrating session cookies, forging administrative requests to modify site content, creating new admin accounts, or pivoting to deliver malware to site visitors.

Root Cause

The root cause is missing or insufficient output encoding of the sLangEdit GET parameter before it is written into an HTML response. The application trusts user-controlled input for rendering, violating the standard CWE-79 neutralization requirement.

Attack Vector

The attack vector is network-based and requires user interaction. The attacker constructs a URL targeting the Quick.CMS admin endpoint with a malicious value in the sLangEdit query parameter. The victim must be an authenticated administrator for the payload to reach a session with meaningful privileges.

The vulnerability manifests when the vulnerable admin script reflects the sLangEdit value into the HTML response without escaping HTML metacharacters. See the CERT Poland advisory for additional technical context on the disclosure.

Detection Methods for CVE-2025-55175

Indicators of Compromise

HTTP requests to Quick.CMS admin endpoints containing sLangEdit= with HTML or JavaScript characters such as <script, onerror=, javascript:, or URL-encoded equivalents (%3Cscript)
Referer headers on admin requests pointing to unexpected external domains, indicating a link-based lure
Outbound requests from administrator browsers to unknown domains shortly after visiting an admin URL, consistent with cookie exfiltration

Detection Strategies

Deploy web application firewall (WAF) rules that inspect query parameters for XSS payload patterns and block requests targeting sLangEdit
Review web server access logs for GET requests to admin URLs containing suspicious characters in sLangEdit
Correlate admin session activity with anomalous administrative actions such as unexpected account creation or template changes

Monitoring Recommendations

Enable full URI logging on the reverse proxy or web server in front of Quick.CMS to preserve query strings for forensic review
Alert on admin panel access from unusual geolocations, user agents, or Referer values
Monitor for new or modified administrator accounts and configuration changes following admin logins

How to Mitigate CVE-2025-55175

Immediate Actions Required

Restrict access to the Quick.CMS administrator panel by IP allowlist or VPN to reduce exposure to network-based lures
Instruct administrators to avoid clicking untrusted links while authenticated to the CMS and to use a dedicated browser profile for admin work
Audit recent administrator activity and web logs for evidence of exploitation attempts against sLangEdit

Patch Information

At the time of publication, no vendor advisory or patched version has been published for CVE-2025-55175. The CERT Poland disclosure notes that the vendor did not respond with vulnerable version details. Monitor the Opensolution website for updated Quick.CMS releases and apply them as soon as they are available.

Workarounds

Add WAF or reverse-proxy rules that reject requests to admin endpoints where sLangEdit contains <, >, ", ', or script
Enforce a strict Content Security Policy (CSP) on the admin panel to block inline script execution and untrusted script sources
Set the HttpOnly and SameSite=Strict attributes on administrator session cookies to reduce impact if script execution occurs
Require administrators to re-authenticate for sensitive actions to limit damage from hijacked sessions

bash

# Example NGINX rule to block obvious XSS payloads in sLangEdit
if ($arg_sLangEdit ~* "(<|%3C|script|onerror|javascript:)") {
    return 403;
}

# Example CSP header for the admin panel response
add_header Content-Security-Policy "default-src 'self'; script-src 'self'; object-src 'none'; base-uri 'self'" always;