Use-After-Free (UAF), Out-Of-Bounds (OOB) and Write-What-Where (WWW) are the next frontier to reach for memory allocators.
Yet, SLIMalloc (faster and more constant than JEmalloc and TCmalloc despite having many more new desirable features, and in particular, security features) provides a FIX since 2020:
SLIMalloc would bring FireFox to the next level (of speed, resilience and trustworthiness) for many users.