Summary

Assume you have a .tar.gz file uploaded in the Downloads section of a Bitbucket repo.
Downloading this file from Chrome, will give an unzipped file.

Steps to Reproduce

1. Create a file locally, e.g. myfile.txt
2. Zip this file with the command

   tar -czf myfile.tar.gz myfile.txt

3. Running the file command on this zipped file, we see:

   $ file myfile.tar.gz
   myfile.tar.gz: gzip compressed data, last modified: Tue Sep 24 14:51:58 2019, from Unix

4. Upload the file myfile.tar.gz in the Downloads section of a Bitbucket repo
5. Download the file using Chrome

Expected Results

Running the file command on the downloaded file, we should see that it's a gzip file, like this:

$ file myfile.tar.gz
myfile.tar.gz: gzip compressed data, last modified: Tue Sep 24 14:51:58 2019, from Unix

Actual Results

When downloading the file from Chrome and run the file command, we see the following:

$ file myfile.tar.gz
myfile.tar.gz: POSIX tar archive

Notes

The issue seems to be specific to Chrome.
If we download the file from another browser, e.g. Firefox, the downloaded file shows as a gzip file.
Also, downloading a .tar.gz from a website other than Bitbucket, using Chrome, also gives a gzip file.

Workaround

Use a different supported browser