The Toocheke Companion plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to, and including, 2.10 via the 'series_bg_color' post meta field. This is due to insufficient input sanitization in the toocheke_series_bg_color_save() function (which stores the raw $_POST value in post meta) and insufficient output escaping in the series admin column rendering (where the stored value is concatenated into a style attribute without esc_attr()). This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user, such as an administrator, accesses the series list table in the admin dashboard.