User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:74.0) Gecko/20100101 Firefox/74.0

Steps to reproduce:

Clicked a link to download a pdf document.

Actual results:

Multiple tabs are opened infinitely until something crashes.

Expected results:

pdf file downloads

Does this also happen with all add-ons disabled and a fresh user profile?

Clicked a link to download a pdf document.

On an HTML page? In the Firefox Preferences, what is set for PDF files under "Applications"? If it is not set to "Always ask", does setting it to "Always ask" help?

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

(In reply to Andre Klapper from comment #1)

Does this also happen with all add-ons disabled and a fresh user profile?

Clicked a link to download a pdf document.

On an HTML page? In the Firefox Preferences, what is set for PDF files under "Applications"? If it is not set to "Always ask", does setting it to "Always ask" help?

Yes this was on any html page, change the preference setting to Always ask which gave the prompt. If Firefox is selected from the open with function the issue still occurs, without it automatically opening new tabs as it is now asking every time but if another application is selected, such as chrome, the document opens as expected.