CVE-2020-36912: Plexus Digital Signage Open Redirect

CVE-2020-36912 Overview

CVE-2020-36912 is an open redirect vulnerability affecting Plexus anblick Digital Signage Management version 3.1.13. The vulnerability exists in the PantallaLogin script, which fails to properly validate user-supplied input in the pagina GET parameter. This allows attackers to craft malicious URLs that redirect authenticated users to arbitrary external websites, potentially facilitating phishing attacks, credential theft, or malware distribution.

Critical Impact

Attackers can exploit this open redirect to deceive users into visiting malicious websites, leveraging the trust users have in the legitimate application domain to conduct phishing campaigns or distribute malware.

Affected Products

• Plexus anblick Digital Signage Management 3.1.13

Discovery Timeline

• 2026-01-06 - CVE CVE-2020-36912 published to NVD
• 2026-01-08 - Last updated in NVD database

Technical Details for CVE-2020-36912

Vulnerability Analysis

This open redirect vulnerability (CWE-601) occurs when the application accepts a user-controlled parameter intended to specify a redirect destination but fails to validate whether that destination is a trusted URL. In the case of Plexus anblick Digital Signage Management 3.1.13, the PantallaLogin script accepts a pagina GET parameter that determines where users are redirected after certain actions. The lack of input validation allows attackers to inject arbitrary URLs into this parameter, causing the application to redirect users to attacker-controlled websites.

Open redirect vulnerabilities are particularly dangerous because they abuse the trust relationship between users and legitimate domains. When a victim clicks a link that appears to point to a trusted domain, they may not notice they are being redirected to a malicious site. This makes such vulnerabilities highly effective for phishing attacks, session hijacking attempts, and malware delivery.

Root Cause

The root cause of CVE-2020-36912 is improper input validation in the PantallaLogin script. The application does not implement proper URL validation or whitelisting to ensure the pagina parameter only accepts internal or trusted redirect destinations. Without server-side validation against a predefined list of allowed URLs or proper URL parsing to verify the destination domain, attackers can inject arbitrary external URLs that the application will blindly redirect users to.

Attack Vector

The attack vector for this vulnerability is network-based and requires user interaction. An attacker crafts a malicious URL containing the vulnerable endpoint with a specially crafted pagina parameter pointing to an attacker-controlled website. The attacker then distributes this link through phishing emails, social media, or other channels. When a victim clicks the link, they are initially directed to the legitimate Plexus anblick Digital Signage Management application, which then immediately redirects them to the malicious destination.

The attacker-controlled destination could host a convincing phishing page mimicking the legitimate login interface to harvest credentials, serve malware payloads, or execute further social engineering attacks. Since the initial URL appears legitimate and originates from a trusted domain, victims are more likely to trust the redirected content.

Detection Methods for CVE-2020-36912

Indicators of Compromise

• HTTP requests to the PantallaLogin endpoint containing suspicious pagina parameters with external URLs
• Redirect responses (HTTP 302/301) from the application pointing to unfamiliar or suspicious external domains
• User reports of unexpected redirects when accessing the digital signage management interface
• Web server logs showing unusual patterns of requests with encoded or obfuscated URLs in the pagina parameter

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests with external URLs in the pagina parameter
• Configure web server logging to capture full query strings and monitor for suspicious redirect patterns
• Deploy network monitoring solutions to identify unexpected outbound connections following application access
• Use SIEM correlation rules to detect multiple redirect attempts from the same source IP address

Monitoring Recommendations

• Regularly review web application logs for anomalous pagina parameter values in requests to PantallaLogin
• Set up alerts for redirect responses that contain external domains not on an approved whitelist
• Monitor user behavior analytics for unusual navigation patterns that may indicate exploitation attempts
• Implement URL reputation checking for destinations in redirect parameters

How to Mitigate CVE-2020-36912

Immediate Actions Required

• Implement server-side validation for the pagina parameter to only accept internal or whitelisted URLs
• Deploy a web application firewall (WAF) rule to block requests with external URLs in redirect parameters
• Educate users about the risks of clicking links from untrusted sources, even if they appear to point to known domains
• Review access logs for any historical exploitation attempts

Patch Information

No vendor patch information is currently available for CVE-2020-36912. Organizations should contact Plexus directly for remediation guidance. Additional technical details can be found in the Zero Science Lab Advisory ZSL-2020-5573, the IBM X-Force Vulnerability Database, and the VulnCheck Advisory.

Workarounds

• Implement a reverse proxy or WAF rule to strip or validate the pagina parameter before requests reach the application
• Restrict access to the digital signage management interface to trusted networks using network segmentation or VPN requirements
• Deploy Content Security Policy (CSP) headers to limit where the application can redirect users
• Consider disabling the redirect functionality entirely if not essential to business operations

# Example WAF rule to block external redirects (ModSecurity syntax)
SecRule ARGS:pagina "@rx ^https?://" \
    "id:100001,\
    phase:1,\
    deny,\
    status:403,\
    log,\
    msg:'Blocked potential open redirect attempt in pagina parameter',\
    tag:'CVE-2020-36912'"