User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:58.0) Gecko/20100101 Firefox/58.0 Build ID: 20171020221129 Steps to reproduce: Opening any pdf will start a recursive loop of opening new tabs with the same pdf. I know this works fine for everyone else that i know have tried the new nightly build, so this might be hairy to fix. It even works fine on my other computer. I've tried reinstalling, but it didn't fix it. My current laptop is a Dell XPS 15. Actual results: Here is a gifv to show the issue: https://i.imgur.com/snK0ZYl.gifv Expected results: It should've openend just one tab.

Have you tried setting PDF files to "Preview in Nightly"?

Thank you very much, this resolved the issue :)