CVE-2026-8905 in Osiris Signature Banner Plugin
Summary
by MITRE • 06/24/2026
The Osiris Signature Banner plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 0.5. This is due to missing or incorrect nonce validation on a function. This makes it possible for unauthenticated attackers to update settings and inject malicious web scripts via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.
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Analysis
by VulDB Data Team • 06/24/2026
The Osiris Signature Banner plugin for WordPress presents a critical cross-site request forgery vulnerability that affects all versions up to and including 050. This weakness stems from inadequate nonce validation within the plugin's core functionality, creating a significant security gap that adversaries can exploit without authentication requirements. The vulnerability resides in the plugin's handling of administrative actions where proper cryptographic tokens intended to verify legitimate requests are either absent or improperly validated. This flaw operates under the principle that attackers can manipulate user sessions through forged requests, specifically targeting the plugin's settings update mechanisms that control banner display configurations and associated parameters.
The technical implementation of this CSRF vulnerability occurs when an unauthenticated attacker crafts malicious requests that appear to originate from legitimate administrative users. The plugin fails to validate the authenticity of incoming requests through proper nonce verification, allowing attackers to manipulate critical settings such as banner content, positioning parameters, and other configuration options. This weakness directly maps to CWE-352, which defines Cross-Site Request Forgery vulnerabilities as those where applications fail to validate the origin or authenticity of requests. The vulnerability creates a pathway for attackers to inject malicious web scripts into the plugin's functionality, potentially leading to persistent cross-site scripting attacks that can compromise user sessions and access sensitive data.
Operational impact of this vulnerability extends beyond simple configuration manipulation, as it enables attackers to establish persistent malicious presence within WordPress installations. When administrators inadvertently click on malicious links or visit compromised websites, they unknowingly execute forged requests that update plugin settings and potentially inject malicious code into banner display areas. This creates a vector for more sophisticated attacks including session hijacking, credential theft through malicious redirects, and potential privilege escalation if the compromised plugin has elevated permissions within the WordPress environment. The attack surface is particularly concerning because it leverages social engineering tactics that require minimal technical expertise to execute successfully.
Mitigation strategies for this CSRF vulnerability must address both immediate remediation and long-term security hardening measures. Immediate action involves updating to patched versions of the Osiris Signature Banner plugin where proper nonce validation has been implemented, though organizations should verify that the updated versions have been properly tested for compatibility with existing installations. The implementation of additional security controls including content security policies, proper request origin verification, and regular security audits of WordPress plugins provides comprehensive protection against similar vulnerabilities. Organizations should also implement user education programs to prevent administrators from clicking on suspicious links and establish monitoring procedures to detect unauthorized configuration changes in plugin settings. This vulnerability demonstrates the critical importance of maintaining current security practices and the necessity of applying security patches promptly when vulnerabilities are identified in widely deployed web applications.