Description

The Avada Builder (fusion-builder) plugin for WordPress is vulnerable to Unauthenticated Remote Code Execution via PHP Function Injection in versions up to and including 3.15.2. This is due to the `wp_conditional_tags` case in `Fusion_Builder_Conditional_Render_Helper::get_value()` passing attacker-controlled values from a base64-decoded JSON blob directly to `call_user_func()` without any allowlist validation. This is exploitable by unauthenticated attackers through the `fusion_get_widget_markup` AJAX endpoint, which is registered for non-privileged (unauthenticated) users via `wp_ajax_nopriv_fusion_get_widget_markup`. The endpoint is protected only by a nonce (`fusion_load_nonce`), but this nonce is generated for user ID 0 and is deterministically exposed in the JavaScript output of any public-facing page containing a Post Cards (`[fusion_post_cards]`) or Table of Contents (`[fusion_table_of_contents]`) element. This makes it possible for unauthenticated attackers to execute arbitrary code on affected sites.

Weaknesses 1

References 12

• avada.com https://avada.com/documentation/avada-changelog/
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/fusion-builder/tags/3.15.0/inc/class-fusion-builder.php#L7551
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/fusion-builder/tags/3.15.0/inc/helpers/class-fusion-builder-conditional-render-helper.php#L1083
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/fusion-builder/tags/3.15.0/inc/helpers/class-fusion-builder-conditional-render-helper.php#L1531
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/fusion-builder/tags/3.15.0/shortcodes/fusion-widget.php#L389
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/fusion-builder/tags/3.15.0/shortcodes/fusion-widget.php#L44
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/fusion-builder/trunk/inc/class-fusion-builder.php#L7551
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/fusion-builder/trunk/inc/helpers/class-fusion-builder-conditional-render-helper.php#L1083
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/fusion-builder/trunk/inc/helpers/class-fusion-builder-conditional-render-helper.php#L1531
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/fusion-builder/trunk/shortcodes/fusion-widget.php#L389
• plugins.trac.wordpress.org https://plugins.trac.wordpress.org/browser/fusion-builder/trunk/shortcodes/fusion-widget.php#L44
• wordfence.com https://www.wordfence.com/threat-intel/vulnerabilities/id/5dc72d78-d47c-4b36-8d69-8672e15ddf8c?source=cve

Remediation