CVE-2025-5528 is a reflected Cross-Site Scripting (XSS) vulnerability identified in the Social Sharing Plugin – Sassy Social Share for WordPress, developed by heateor. This vulnerability affects all versions up to and including 3.3.75. The root cause is insufficient input sanitization and output escaping of the 'heateor_mastodon_share' parameter. An unauthenticated attacker can craft a malicious URL containing a payload in this parameter. When a user clicks on such a link and loads a page containing this plugin, the injected script executes in the context of the victim's browser. This reflected XSS does not require authentication but does require user interaction (clicking a malicious link). The vulnerability impacts confidentiality and integrity by enabling attackers to steal session cookies, perform actions on behalf of the user, or redirect users to malicious sites. The CVSS v3.1 base score is 6.1 (medium severity), reflecting network attack vector, low attack complexity, no privileges required, user interaction required, and partial confidentiality and integrity impact without availability impact. No known exploits are currently in the wild, and no patches have been linked yet. Given the widespread use of WordPress and the popularity of social sharing plugins, this vulnerability poses a significant risk to websites using this plugin, especially those with high user interaction or sensitive data.

For European organizations, the impact of this vulnerability can be substantial, particularly for businesses and institutions relying on WordPress websites with the Sassy Social Share plugin enabled. Attackers could exploit this flaw to hijack user sessions, steal sensitive information, or conduct phishing attacks by injecting malicious scripts. This can lead to reputational damage, loss of customer trust, and potential regulatory penalties under GDPR if personal data is compromised. E-commerce platforms, government portals, and media websites are especially at risk due to their high traffic and user engagement. The reflected XSS can also be used as a stepping stone for more complex attacks, including delivering malware or conducting targeted social engineering campaigns. Since the vulnerability requires user interaction, organizations with less tech-savvy users may face higher exploitation risks. Additionally, the lack of a patch at the time of disclosure means organizations must rely on mitigation strategies until an official update is released.

1. Immediate mitigation should include disabling or removing the Sassy Social Share plugin until a patched version is available. 2. Implement Web Application Firewall (WAF) rules to detect and block malicious payloads targeting the 'heateor_mastodon_share' parameter. 3. Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts on affected pages. 4. Educate users and administrators about the risks of clicking unknown or suspicious links, especially those containing unusual URL parameters. 5. Monitor web server logs for unusual requests containing suspicious 'heateor_mastodon_share' parameter values. 6. Once a patch is released, prioritize updating the plugin to the fixed version. 7. Conduct regular security audits and vulnerability scans on WordPress installations to identify outdated or vulnerable plugins. 8. Consider implementing input validation and output encoding at the application level if customizations exist around the plugin.