The SiteOrigin Widgets Bundle plugin for WordPress suffers from a stored cross-site scripting vulnerability (CWE-79) due to improper neutralization of input in the onclick parameter. Authenticated users with contributor or higher roles can inject malicious JavaScript code that executes in the context of other users viewing the compromised pages. This vulnerability affects all versions up to and including 1.58.3, with 1.58.3 offering only a partial remediation. The CVSS 3.1 base score is 6.4, reflecting network attack vector, low attack complexity, privileges required, no user interaction, and impacts on confidentiality and integrity with scope change.

An attacker with contributor or higher privileges can inject persistent malicious scripts via the onclick parameter, which execute in the browsers of users who visit the affected pages. This can lead to unauthorized actions performed on behalf of users, data disclosure, or session hijacking. The vulnerability does not impact availability. No known active exploitation has been reported.

No full patch or official fix is currently confirmed. Version 1.58.3 includes a partial fix but does not fully resolve the issue. Users should monitor the vendor's advisory for updates and apply any forthcoming official patches promptly. Until a complete fix is available, restrict contributor-level access carefully and consider additional input validation or output encoding measures where possible.