The Twilio integration webhook handler accepts any POST request without validating Twilio's 'X-Twilio-Signature'. When processing media messages, it fetches user-controlled URLs ('MediaUrlN' parameters) using HTTP requests that include the integration's Twilio credentials in the 'Authorization' header. An attacker can forge a webhook payload pointing to their own server and receive the victim's 'accountSID' and 'authToken' in plaintext (base64-encoded Basic Auth), leading to full compromise of the Twilio account.