CVE-2026-1902 is a stored Cross-Site Scripting (XSS) vulnerability identified in the innovaatik Hammas Calendar plugin for WordPress, present in all versions up to and including 1.5.11. The vulnerability stems from improper neutralization of input during web page generation, specifically involving the 'apix' parameter within the 'hp-calendar-manage-redirect' shortcode. Due to insufficient input sanitization and lack of proper output escaping, authenticated users with Contributor-level permissions or higher can inject arbitrary JavaScript code into pages managed by the plugin. This malicious script is stored persistently and executes whenever any user accesses the compromised page, potentially allowing attackers to hijack user sessions, steal cookies, or perform actions on behalf of other users. The vulnerability has a CVSS 3.1 base score of 6.4, reflecting medium severity, with an attack vector of network, low attack complexity, requiring privileges (PR:L), no user interaction, and a scope change (S:C). The impact affects confidentiality and integrity but not availability. No patches or official fixes are currently linked, and no known exploits have been reported in the wild. The vulnerability is significant because WordPress sites often rely on plugins for calendar and event management, and Contributor-level access is commonly granted to trusted users, making this a plausible attack vector for insider threats or compromised accounts.

The primary impact of CVE-2026-1902 is the potential for attackers with Contributor-level access to inject persistent malicious scripts into WordPress sites using the Hammas Calendar plugin. This can lead to session hijacking, theft of sensitive user information such as cookies or authentication tokens, and unauthorized actions performed on behalf of legitimate users. Since the injected scripts execute in the context of the victim's browser, it can facilitate further attacks like privilege escalation or lateral movement within the WordPress environment. Although availability is not directly affected, the compromise of user accounts and data confidentiality can severely damage organizational reputation and trust. For organizations relying on WordPress for public-facing websites or internal portals, this vulnerability could be exploited to target site administrators or users with elevated privileges, potentially leading to broader compromise of the web infrastructure. The requirement for authenticated access limits the attack surface but does not eliminate risk, especially in environments with multiple contributors or where account credentials may be compromised.

To mitigate CVE-2026-1902, organizations should first check for updates from innovaatik and apply any available patches or plugin updates that address this vulnerability. In the absence of an official patch, administrators should consider temporarily disabling the Hammas Calendar plugin or restricting Contributor-level access until a fix is available. Implementing strict input validation and output encoding for the 'apix' parameter within the plugin code can prevent script injection; this may require custom code review and modification by developers. Additionally, monitoring user activity logs for unusual Contributor behavior and employing Web Application Firewalls (WAFs) with rules to detect and block XSS payloads targeting the affected shortcode can reduce risk. Enforcing multi-factor authentication (MFA) for all WordPress accounts with elevated privileges can help prevent unauthorized access that could lead to exploitation. Regular security audits and user permission reviews will also minimize the likelihood of exploitation by limiting the number of users with Contributor or higher roles.