CVE-2026-28106: B2BKing Premium Open Redirect Vulnerability

CVE-2026-28106 Overview

CVE-2026-28106 is an Open Redirect vulnerability (CWE-601) affecting Kings Plugins B2BKing Premium, a WordPress plugin designed for B2B e-commerce functionality. This vulnerability allows attackers to redirect users from the legitimate WordPress site to malicious external websites, enabling phishing attacks against unsuspecting users who trust the original domain.

Critical Impact

Attackers can leverage this open redirect to conduct phishing campaigns, potentially stealing credentials, financial information, or distributing malware by abusing the trust users have in the legitimate B2BKing-powered website.

Affected Products

• B2BKing Premium versions prior to 5.4.20
• WordPress sites running vulnerable B2BKing Premium plugin installations

Discovery Timeline

• 2026-03-06 - CVE CVE-2026-28106 published to NVD
• 2026-03-09 - Last updated in NVD database

Technical Details for CVE-2026-28106

Vulnerability Analysis

This vulnerability stems from improper validation of user-supplied URL parameters within the B2BKing Premium plugin. When the plugin processes redirect requests, it fails to adequately verify that the destination URL belongs to a trusted domain. This allows an attacker to craft malicious links that appear to originate from a legitimate WordPress site but redirect users to attacker-controlled websites.

The attack requires user interaction, as victims must click on the malicious link for the redirect to occur. However, because the initial URL points to a trusted domain, users are more likely to click on such links, especially when received via email or social media.

Root Cause

The root cause of CVE-2026-28106 is insufficient input validation on URL redirect parameters. The plugin accepts external URLs without properly validating the destination against an allowlist of trusted domains. This lack of validation enables attackers to inject arbitrary redirect destinations into plugin functionality.

Attack Vector

The vulnerability is exploited via network-based attacks where the attacker crafts a URL containing a malicious redirect parameter. The attack flow typically involves:

1. Attacker identifies a vulnerable B2BKing Premium endpoint that accepts redirect parameters
2. Attacker constructs a URL pointing to the legitimate site but containing a redirect to a malicious domain
3. The crafted link is distributed via phishing emails, social media, or other channels
4. When a victim clicks the link, they are redirected from the trusted WordPress site to the attacker's phishing page
5. The victim, believing they are still interacting with the legitimate site, may enter sensitive credentials or personal information

The attack does not require authentication and can target any user who accesses the malicious link. For detailed technical information, refer to the Patchstack WordPress Vulnerability Report.

Detection Methods for CVE-2026-28106

Indicators of Compromise

• Unusual redirect patterns in web server access logs showing external domains in redirect parameters
• User reports of being redirected to unexpected websites after clicking internal links
• HTTP request logs containing URL parameters with external domains encoded in base64 or URL-encoded formats
• Phishing reports from users mentioning the organization's domain in the original URL

Detection Strategies

• Implement web application firewall (WAF) rules to detect and block requests containing suspicious redirect parameters with external domains
• Monitor server logs for requests to B2BKing plugin endpoints that include URL parameters pointing to external domains
• Deploy browser-based detection tools to identify redirect chains originating from the WordPress site

Monitoring Recommendations

• Enable verbose logging on WordPress installations to capture all redirect-related activity
• Set up alerts for spikes in traffic to plugin endpoints commonly associated with redirect functionality
• Monitor for brand abuse and phishing sites that may be leveraging your domain's reputation through open redirect attacks

How to Mitigate CVE-2026-28106

Immediate Actions Required

• Update B2BKing Premium plugin to version 5.4.20 or later immediately
• Review web server logs for evidence of exploitation attempts
• Notify users if there is evidence of successful phishing attacks leveraging this vulnerability
• Consider temporarily disabling redirect functionality if immediate patching is not possible

Patch Information

Kings Plugins has addressed this vulnerability in B2BKing Premium version 5.4.20. Administrators should update to this version or later to remediate the open redirect vulnerability. The patch implements proper validation of redirect destinations to ensure only trusted URLs are accepted.

For additional details about the vulnerability and patch, see the Patchstack WordPress Vulnerability Report.

Workarounds

• Implement server-level URL rewrite rules to block redirect parameters containing external domains
• Deploy a WAF with rules to filter requests containing suspicious redirect patterns
• Use a content security policy (CSP) to restrict navigation to untrusted domains, though this may not fully prevent server-side redirects

# Example Apache .htaccess rule to block external redirects in query parameters
RewriteEngine On
RewriteCond %{QUERY_STRING} (redirect|url|return|next)=https?:// [NC]
RewriteRule .* - [F,L]