CVE-2026-13203: Live Composer <= 2.1.19 - Authenticated (Contributor+) Stored Cross-Site Scripting via 'custom_id' Shortcode Attribute

The Live Composer – Free WordPress Website Builder plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'customid' shortcode attribute of the dslcmodulessection and dslcmodulesarea shortcodes in versions up to, and including, 2.1.19. This is due to insufficient input sanitization and output escaping on the user-supplied attribute, which is concatenated into the HTML id="" attribute of the rendered <div> element in the dslcmodulessectionfront() and dslcmodulesareafront() functions without escattr(). 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.