This issue should be fixed in 48.0.2, many crashes like yours are due to Websense Endpoint. Do you have this software installed on your machine?

I do have the Websense Endpoint on my machine, but this crashing issue just recently started, and 48.0.2 was automatically installed right before this started.

Add on: I attempted to downgrade to 48.0.1 and it didn't resolve my issue.

Mozilla has reopened the bug report about Websense crashing Firefox so the issue is probably not fully fixed with 48.0.2. :/

Wensense has fixed the issue in version 8.2.5. Can you try to update Websense?

There are some Websense versions before 8.1 which are causing startup crashes on Firefox 48 and 49. Websense is suggesting that affected users should update to the latest version of their software, or ask their IT admin to update across their organization. This document from Forcepoint outlines their supported versions for each browser: https://support.forcepoint.com/KBArticle?id=TRITON-AP-ENDPOINT-Browser-Certified-Product-Matrix