CVE-2026-50740: Revive Adserver XSS Vulnerability

CVE-2026-50740 Overview

CVE-2026-50740 is a reflected Cross-Site Scripting (XSS) vulnerability in Revive Adserver versions 6.0.7 and earlier. The flaw resides in the zone-include.php script, which fails to sanitize user input passed through the refresh parameter of the iFrame invocation tag. A low-privileged authenticated user can craft a malicious refresh parameter value that reflects unescaped script content back to a victim's browser. Successful exploitation requires user interaction, and impact crosses trust boundaries because the injected script executes in the context of the ad server domain. This vulnerability is tracked under CWE-79: Improper Neutralization of Input During Web Page Generation.

Critical Impact
An authenticated attacker can execute arbitrary JavaScript in a victim's browser session, enabling session theft, ad campaign tampering, and phishing against Revive Adserver administrators.

Affected Products

Revive Adserver 6.0.7
All Revive Adserver versions prior to 6.0.7
Deployments exposing the iFrame invocation tag with the refresh parameter

Discovery Timeline

2026-06-26 - CVE-2026-50740 published to NVD
2026-06-29 - Last updated in NVD database

Technical Details for CVE-2026-50740

Vulnerability Analysis

Revive Adserver generates ad invocation tags that clients embed in web pages to load ads. The zone-include.php script produces iFrame-based invocation code and accepts a refresh parameter controlling how often the iFrame reloads. The script fails to properly neutralize user-supplied input before reflecting it back inside the generated HTML response. An authenticated user with low privileges can supply crafted JavaScript payloads through the refresh parameter, and the server returns those payloads inside HTML attributes or script contexts without encoding. Because the vulnerability changes scope, the injected script runs against another user's browser session, typically an administrator viewing generated tags or a visitor of a page embedding the tag.

Root Cause

The root cause is missing output encoding on the refresh request parameter inside zone-include.php. The parameter value is treated as trusted numeric data but flows into an HTML response without HTML entity encoding, attribute escaping, or type validation. A strict integer cast or a whitelist regex on refresh would have prevented injection.

Attack Vector

Exploitation follows a standard reflected XSS pattern. The attacker crafts a URL containing a malicious payload in the refresh query parameter of the iFrame invocation endpoint. The attacker then lures a victim, typically an authenticated Revive Adserver user or an end user of a site consuming the invocation code, to click the link. The server returns HTML containing the unsanitized payload, and the victim's browser executes the injected script under the ad server's origin. This enables session cookie theft, cross-site request forgery against the Revive administration interface, and manipulation of ad delivery. See the HackerOne Report #3780806 for reporter details.

Detection Methods for CVE-2026-50740

Indicators of Compromise

HTTP GET requests to zone-include.php where the refresh parameter contains characters such as <, >, ", ', or the substrings script, onerror, onload, or javascript:.
Web server access logs showing abnormally long or URL-encoded refresh values that do not conform to expected numeric input.
Referer headers pointing to attacker-controlled domains in requests targeting invocation tag endpoints.

Detection Strategies

Deploy Web Application Firewall (WAF) rules that inspect the refresh parameter on Revive Adserver endpoints and block non-numeric content.
Enable Content Security Policy (CSP) violation reporting to surface unexpected inline script execution on ad server pages.
Correlate authentication events for low-privileged Revive users with subsequent access to zone-include.php containing suspicious query strings.

Monitoring Recommendations

Alert on any HTTP 200 response from zone-include.php where the response body reflects the raw refresh query value without encoding.
Monitor administrator sessions for unexpected origin changes, cookie exports, or CSRF-style state-changing requests immediately following ad tag previews.
Track outbound requests from browsers rendering Revive Adserver pages to unknown domains that could indicate exfiltration by injected scripts.

How to Mitigate CVE-2026-50740

Immediate Actions Required

Upgrade Revive Adserver to a version later than 6.0.7 as soon as a fixed release is available from the Revive Adserver project.
Restrict access to the Revive administration interface to trusted networks or VPN users to limit low-privileged account abuse.
Review recently generated invocation tags for suspicious refresh values and rotate administrative session cookies.

Patch Information

At the time of publication, refer to the vendor's security advisories and the HackerOne Report #3780806 for the fixed version. Apply the patched release across all Revive Adserver instances, then invalidate active sessions and force password resets for accounts with tag generation privileges.

Workarounds

Deploy a WAF rule that rejects requests to zone-include.php unless the refresh parameter matches ^[0-9]+$.
Apply a strict Content Security Policy that disallows inline scripts and restricts script sources on ad server responses.
Temporarily disable the iFrame invocation tag generation feature for low-privileged accounts until the upgrade is complete.

bash

# Example ModSecurity rule enforcing numeric refresh parameter
SecRule REQUEST_URI "@contains zone-include.php" \
  "chain,phase:2,deny,status:400,id:1026050740,\
  msg:'CVE-2026-50740 - Non-numeric refresh parameter blocked'"
  SecRule ARGS:refresh "!@rx ^[0-9]{1,6}$" "t:none"