CVE-2024-13670 is a stored cross-site scripting vulnerability in the efreja Music Sheet Viewer WordPress plugin (versions up to 4.1). It occurs due to improper neutralization of input in the 'pn_msv' shortcode, where user-supplied attributes are not adequately sanitized or escaped. Authenticated attackers with contributor or higher privileges can inject arbitrary web scripts that execute in the context of users visiting the injected pages. This vulnerability can lead to limited confidentiality and integrity impacts but does not affect availability. The CVSS 3.1 base score is 6.4 (AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N).

An attacker with contributor-level or higher access can inject persistent malicious scripts into pages via the vulnerable shortcode. These scripts execute in the browsers of users who visit the compromised pages, potentially leading to theft of user data or session tokens (confidentiality impact) and unauthorized modification of displayed content (integrity impact). There is no direct impact on system availability. The vulnerability requires authenticated access, limiting exploitation scope.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, restrict contributor-level access to trusted users only and consider disabling or removing the Music Sheet Viewer plugin if possible. Monitor for plugin updates from efreja that address this vulnerability.