Firefox 52 has introduced a regression where
XMLHttpRequest retrieving large data with the
blob response type results in a corrupt file in certain cases. The issue would likely occur with files more than 10 MB due to a race condition, and can be avoided, according to the bug reporter, by setting the response type to
moz-blob. Mozilla developers are working on the solution.
Update: This issue has been fixed with Firefox 53 and Firefox ESR 52.1.