Exercises page PDF doesn't show up in FireFox on Windows

[alexgleason]

On Norm's computer we couldn't get the PDF to render in the exercises page. I've just tested it in FireFox on Windows 7 and it showed up fine. Trying to pinpoint what exactly was happening on Norm's computer so we can handle it. At worst, we might have to rethink how we're embedding PDFs.

I've set Content-Disposition: inline in the HTTP header of the PDF. One would think this is enough. I'm trying to reproduce the problem, but can't.

It was happening at this URL (and others like it): https://project-tier-dev.herokuapp.com/tier-classroom/sample-exercises/sample-exercises/alcohol-exercise/

[alexgleason]

Norm is running Windows 10 and Firefox 59.0.2 (64-bit). Using BrowserStack I'm running FireFox 59 on Windows 10 and seeing this:

The difficult thing about this issue is that I can't reproduce the problem. I witnessed it in person, however. The issue seemed to be that FireFox disobeyed the HTTP attachment key. I inspected the request and observed that is was sending back attachment: inline but despite this it was being downloaded anyway.

Any embed solution I come up with will have the same issue since this is happening on an HTTP level. The only thing I can think of is to embed the files with a third-party service like Google Docs, which in addition to the freedom/privacy implications seems fragile, inflexible, and undesired.

First, I really want to know what is different about Norm's FireFox install compared to the one in BrowserStack. Knowing that could help us address the problem.