The PAC file was a dropper. It had been phoning home every six hours, rewriting itself silently via a cron job on the proxy server. The entire corporate network was feeding its traffic patterns to a C2 server in Eastern Europe.
: You can open these with any standard text editor or a specialized Text Extractor app from the Play Store. How to use pac file extractor apk exclusive
Disclaimer: Modifying firmware carries risks. Always back up your current system. The PAC file was a dropper