The LazyLoad Plugin – Lazy Load Images, Videos, and Iframes plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'comment_content (rendered inline into the page HTML)' parameter in all versions up to, and including, 2.4.0 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. WordPress core's wp_kses_data allow-list does not strip the crafted payload on save because it uses only permitted tags and attributes; the event handler is concealed inside a broken attribute region and is only promoted to a real DOM attribute by the plugin's render-time str_replace transformation. Additionally, a site administrator must approve the crafted comment before the payload is served to other visitors.
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