Most vendors that offer bug bounties offer them based on the ability to exploit a vulnerability in such a manner that could lead to "code execution", "data loss" or something along those lines. Most vendors will tell you "what" they are looking for with their bug bounty programs in their FAQs. Crashing a browser is more of a DoS, developer issue versus an exploitable (oh you can trigger code execution!) one.
So that answers your question but just in case, here is Mozilla's FAQ:
- Security bug must be original and previously unreported.
- Security bug must be a remote exploit, compromise user data, allow
access to Mozilla infrastructure or resources, or easily manipulate a
- Submitter must not be the author of the buggy code nor otherwise
involved in its contribution to the Mozilla project (such as by
providing check-in reviews).
- Employees of the Mozilla Foundation and its subsidiaries are