CVE-2026-2354 describes a file upload vulnerability in the Swiss Toolkit For WP plugin for WordPress versions up to and including 1.4.6. The vulnerability arises from flawed file type validation in the `upload_extension_files()` function, which hooks into WordPress's `wp_check_filetype_and_ext` filter. Instead of properly validating the file extension, it uses `strpos()` to check if the filename contains a configured extension string, enabling an authenticated attacker with Author-level privileges or higher to bypass restrictions and upload arbitrary files, including PHP scripts. If the plugin's "Enhanced Multi-Format Image Support" feature is enabled with at least one allowed extension, this can lead to remote code execution on the affected server.

An attacker with Author-level access or higher can upload arbitrary files, including executable PHP files, to the affected WordPress site. This can lead to full compromise of the site through remote code execution, data theft, or site defacement. The vulnerability affects confidentiality, integrity, and availability of the affected system. The CVSS v3.1 base score is 8.8 (High), reflecting network attack vector, low attack complexity, required privileges, no user interaction, and high impact on confidentiality, integrity, and availability.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Until an official fix is released, restrict Author-level access to trusted users only and consider disabling the "Enhanced Multi-Format Image Support" feature if enabled. Monitor for plugin updates from wpmessiah and apply them promptly once available.