The Autoptimize plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the LCP Image to preload metabox in all versions up to, and including, 3.1.13 due to insufficient input sanitization and output escaping on user-supplied image attributes in the "create_img_preload_tag" function. 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.