CVE-2025-9849 is a medium-severity Stored Cross-Site Scripting (XSS) vulnerability affecting the Html Social share buttons plugin for WordPress, developed by alimuzzamanalim. This vulnerability exists in all versions up to and including 2.1.16 due to improper input sanitization and output escaping of user-supplied attributes in the plugin's 'zm_sh_btn' shortcode. Specifically, authenticated users with contributor-level access or higher can inject arbitrary JavaScript code into pages via crafted shortcode attributes. When other users visit these compromised pages, the injected scripts execute in their browsers under the context of the vulnerable site. The vulnerability arises from CWE-79: Improper Neutralization of Input During Web Page Generation, a common web application security flaw that enables attackers to bypass input validation and embed malicious scripts. The CVSS v3.1 base score is 5.3, reflecting a medium severity level, with an attack vector of network (remote exploitation), low attack complexity, no privileges required (beyond contributor access), no user interaction needed for exploitation, and impact limited to integrity (no confidentiality or availability impact). No known exploits are currently reported in the wild. The vulnerability is particularly concerning because contributor-level users are often trusted content creators, and this flaw allows them to escalate their impact by injecting scripts that affect other users, potentially leading to session hijacking, defacement, or distribution of malware through the affected WordPress sites.

For European organizations using WordPress sites with the Html Social share buttons plugin, this vulnerability poses a risk of unauthorized script execution within the context of their websites. This can lead to compromised user sessions, defacement, or the delivery of malicious payloads to visitors, undermining trust and potentially violating data protection regulations such as GDPR if personal data is exposed or manipulated. Organizations relying on contributor-level users to add content are at particular risk, as these users can exploit the vulnerability to inject malicious code. The impact is primarily on the integrity of the website content and user interactions, which can damage brand reputation and lead to financial losses through remediation costs and potential regulatory fines. Since the vulnerability does not affect confidentiality or availability directly, the risk is somewhat contained but still significant given the widespread use of WordPress in Europe. Additionally, the lack of known public exploits suggests that proactive patching and mitigation can effectively prevent exploitation.

European organizations should immediately audit their WordPress installations to identify the presence of the Html Social share buttons plugin and verify its version. Since no official patches or updates are linked, administrators should consider disabling or removing the plugin until a secure version is released. Restrict contributor-level user permissions to trusted individuals only and implement strict content review workflows to detect and prevent malicious shortcode usage. Employ Web Application Firewalls (WAFs) with rules targeting XSS payloads in shortcode parameters to block exploitation attempts. Additionally, enable Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts on affected sites. Regularly monitor website logs and user activity for suspicious behavior indicative of exploitation. Educate content contributors about secure content practices and the risks of injecting untrusted code. Finally, maintain an up-to-date WordPress core and plugin environment to reduce exposure to known vulnerabilities.