Cross-site scripting in stepasyuk Filter Everything — WordPress & WooCommerce Filters

Summary

The Filter Everything — WordPress & WooCommerce Filters plugin for WordPress is vulnerable to Reflected Cross-Site Scripting in versions up to, and including, 1.9.6. This is due to insufficient input sanitization and output escaping in the flrt_elementor_load_more_anchor() function. The function reads query parameters from $_SERVER['REQUEST_URI'] via getFormActionOrFullPageUrl(true), which URL-decodes them through parse_str() and re-assembles them using build_query() — a WordPress core function that does NOT re-encode values ($urlencode=false). The resulting URL, containing unescaped special characters, is injected into a data-next-page HTML attribute via preg_replace() without esc_attr() or esc_url(). This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a specially crafted link.