The Astra theme for WordPress is vulnerable to Stored Cross-Site Scripting via the ast-page-background-meta and ast-content-background-meta post meta fields in all versions up to, and including, 4.12.3. This is due to insufficient input sanitization on meta registration and missing output escaping in the astra_get_responsive_background_obj() function for four CSS-context sub-properties (background-color, background-image, overlay-color, overlay-gradient). 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 accesses an injected page.