Hardened Malloc is a hardened memory allocator which can be used with many applications to increase security.
According to the author's GitHub description: 
This is a security-focused general purpose memory allocator providing the malloc API along with various extensions. It provides substantial hardening against heap corruption vulnerabilities. The security-focused design also leads to much less metadata overhead and memory waste from fragmentation than a more traditional allocator design. It aims to provide decent overall performance with a focus on long-term performance and memory usage rather than allocator micro-benchmarks. It offers scalability via a configurable number of entirely independently arenas, with the internal locking within arenas further divided up per size class.
Readers who wish to discuss the integration of Hardened Malloc with Kicksecure ™ should refer to this forum thread.
Hardened Malloc is pre-installed.
How-to: Launch Applications with Hardened Malloc
To launch individual systemd services with hardened malloc, add a drop-in systemd configuration snippet.
To launch other applications with Hardened Malloc, the
LD_PRELOAD environment variable must be edited before starting the application. For example, to launch
application-name in this way, run.
All Applications by Default
Note: This action may break numerous applications such as man, apt or Xorg.
It is possible to make all applications use Hardened Malloc as the default memory allocator. To configure this option, the path to the
hardened_malloc.so library must be added to the
/etc/ld.so.preload file. 
It is unknown whether other browsers can benefit from Hardened Malloc.
Other applications might not easily benefit from Hardened Malloc for the same reasons outlined in the browsers section above.
Whether an application can benefit from Hardened Malloc or not depends on technical implementation details of the application in question. Vendors of applications will probably know if their application is compatible with Hardened Malloc. Community wiki contributions are most welcome -- please post any additional vendor Q&As here.
Credits and Source Code
The original source software is maintained by security researcher, Daniel Micay.
This website is the software fork homepage for Hardened Malloc, with a focus on easy installation, added user documentation, and integration with Whonix, Kicksecure, Debian, and other distributions. The Kicksecure ™ software fork source code can be found here. Continuous integration: travis CI
/etc/ld.so.preload.ddrop-in configuration folder support
Tor Browser is also based on Firefox, therefore the following advice equally applies.
LD_PRELOAD='/path/to/libhardened_malloc.so' /path/to/program will do nothing or approximately nothing.
The reason is recompilation is necessary.
To successfully replace Firefox memory allocator you should either use LD_PRELOAD _with_ a --disable-jemalloc build OR Firefox's replace_malloc functionality: https://searchfox.org/mozilla-central/source/memory/build/replace_malloc.h