SiteOrigin Widgets Bundle < 1.75.0 - Authenticated (Contributor+) Arbitrary File Read via LESS Injection via [siteorigin_widget] Shortcode 'value' JSON Instance (design.colors LESS Variable)

Description

The SiteOrigin Widgets Bundle plugin for WordPress is vulnerable to Directory Traversal in all versions up to, and including, 1.74.3 via the get_instance_css function. This makes it possible for authenticated attackers, with contributor-level access and above, to read the contents of arbitrary files on the server, which can contain sensitive information. The widget's normal update()/sanitize_field_input() pipeline — which would reject non-hex color values — is bypassed entirely because the [siteorigin_widget] shortcode handler calls $the_widget->widget() directly on the attacker-supplied decoded JSON instance.