The EmbedPress – Embed PDF, Google Docs, Vimeo, Wistia, Embed YouTube Videos, Audios, Maps & Embed Any Documents in Gutenberg & Elementor plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the EmbedPress widget 'embedpress_pro_twitch_theme ' attribute in all versions up to, and including, 3.9.12 due to insufficient input sanitization and output escaping on user supplied attributes. This makes it possible for authenticated attackers with contributor-level and above permissions to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.