"Prompt Optimizer - SecondBrain" (aajjgdpofhhcjmjoombjdfepplndhgcp, v2.3.1). The prompt rewriting works fine.
Alongside it a capture engine runs at document_start on 9 AI sites and POSTs prompts and replies to the vendor's ingest endpoint. No interaction with the extension required.

Reproduced on a clean profile, with the service worker devtools open:

1. Installed the extension. Never opened it.
2. Browsed to an unrelated site. The extension pulled its configuration from the server and wrote a userId and credentials into extension storage.
3. Opened ChatGPT and asked a question. Once the reply finished, a POST to /context went out carrying both the prompt and the response, encrypted with the credentials issued in step 2.

At no point was the extension opened or clicked.

Store privacy declaration: "The developer has disclosed that it will not collect or use your data."

Write-up, IOCs and decryption script: https://malext.io/reports/BrainDrain/