CVE-2024-13399 identifies a stored Cross-Site Scripting (XSS) vulnerability in the Gosign – Posts Slider Block plugin for WordPress, present in all versions up to and including 1.1.0. The vulnerability arises from improper neutralization of input during web page generation (CWE-79), specifically due to insufficient input sanitization and lack of output escaping in the 'posts-slider-block' component. Authenticated users with Contributor-level access or higher can exploit this flaw by injecting arbitrary JavaScript code into pages that utilize the vulnerable block. When other users visit these pages, the injected scripts execute in their browsers, potentially allowing attackers to steal session cookies, perform actions on behalf of users, or deliver further malicious payloads. The vulnerability does not require user interaction beyond visiting the affected page and has a CVSS v3.1 base score of 6.4, reflecting medium severity. The attack vector is network-based (remote), with low attack complexity and requiring privileges (Contributor or above). The scope is changed because the vulnerability affects other users beyond the attacker. No patches or official fixes are currently linked, and no known exploits have been reported in the wild. Given WordPress's widespread use and the plugin's presence, this vulnerability poses a tangible risk to websites that have enabled this block and allow contributors to add content. The vulnerability highlights the importance of proper input validation and output encoding in plugin development to prevent XSS attacks.

The primary impact of CVE-2024-13399 is the compromise of confidentiality and integrity on affected WordPress sites. Exploitation allows attackers to execute arbitrary JavaScript in the context of the victim’s browser, which can lead to session hijacking, theft of sensitive information, unauthorized actions performed with victim user privileges, and potential site defacement or redirection to malicious sites. Since the vulnerability requires Contributor-level access, attackers must first gain or already have authenticated access, which limits but does not eliminate risk. The scope of impact extends to all users who view the infected pages, potentially including site administrators and visitors. This can damage organizational reputation, lead to data breaches, and facilitate further attacks such as phishing or malware distribution. For organizations relying on WordPress for content management, especially those with multiple contributors, this vulnerability could disrupt operations and erode user trust. The absence of known exploits in the wild reduces immediate risk, but the medium CVSS score and ease of exploitation by authenticated users make timely mitigation critical.

Organizations should immediately audit their WordPress installations to identify the presence of the Gosign – Posts Slider Block plugin and verify the version in use. Since no official patch is currently linked, temporary mitigations include restricting Contributor-level access to trusted users only and reviewing user roles to minimize privilege exposure. Administrators should disable or remove the vulnerable block from pages where possible. Implementing Web Application Firewall (WAF) rules to detect and block suspicious script injection attempts targeting the posts-slider-block can provide additional protection. Monitoring logs for unusual contributor activity or unexpected content changes is advised. Developers and site owners should apply strict input validation and output escaping in custom code and plugins. Once a patch becomes available, prompt updating to the fixed version is essential. Additionally, educating contributors about safe content practices and potential risks can reduce accidental exploitation. Regular backups and incident response plans should be in place to recover from potential compromises.