As long as server software and forum software is kept up-to-date things should be pretty safe. The site is also using a secure certificate which helps protect data sent between the web browsers (on peoples computers) and the server.
I host many sites, about 400 for the past 7 years and none have been hacked because I keep the servers up-to-date and all site software up to date. The simplest things help the most!
The easiest way for a users account to be hacked is due to poor/simple passwords, which a lot of people use. I recommend using hard passwords, ones like
cHq58#6$n@DyHDF7 etc etc. Password generators and scripts would have a hard time cracking a password like that.
Never use the same password twice on the internet either. Use a password generator like the following:
https://identitysafe.norton.com/password-generator/
Use a program like 1Password to remember your passwords.