Looks like TestFlight's S3 bucket, covering the period before and up to when Apple acquired the company, was indexed and scraped, and has leaked to archive.org.

This likely contains every unencrypted binary submitted between 2012 and 2015 to the service — ‘terabytes of data’. Dated February 2015. “…and includes several unreleased Angry Birds games.”

https://www.eurogamer.net/apple-testflight-servers-from-2012-to-2015-leak-containing-terabytes-of-data