User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:92.0) Gecko/20100101 Firefox/92.0

Steps to reproduce:

Requested an email to display in Browser, with FF92 set as default app to do so.

Actual results:

Multiple tabs creation loop, had to close browser. I then lost all my previous session tabs.

Expected results:

Ideally, FF should either render the MHT file properly, OR if it cannot, then at least put a warning out that "This file type is not supported, try WORD or equivalent." I KNOW this was reported with BUG 1718681, BUT I feel that the closure response on that was rather poor and irresponsible, with it still attempting to open the (as yet unsupported) file type. It is a potential security risk (buffer or memory overflows, ability to crash the browser and access information, by using specially crafted payloads, malware injection etc).

About:support details for review if needed.

Background info on the security risk side:
https://hackercombat.com/malformed-mht-file-in-internet-explorer-may-lead-to-file-theft/

this is a very old and well-understood problem, and tracking it yet another time is not necessary.

(In reply to Tony Davis from comment #2)

Background info on the security risk side:
https://hackercombat.com/malformed-mht-file-in-internet-explorer-may-lead-to-file-theft/

This is a very different problem that happens to involve the same filetype. That doesn't mean that the Firefox problem has the same risks or security properties, which it does not.