Considerations for granting read and write privileges to MacHD for "everyone"? What are the potential dangers to be wary of when changing the root drives read/write permission? Specifically, granting "everyone" read/write access?  



E.g. will I be opening up my computer to potential malware attacks/viruses and such? Will I be compromising my system integrity? Will it be easier for me to catastrophically damage or erase my entire system? Am I just being paranoid?

Use case: I've recently installed Avid's Media Composer | First and while I can use external drives (and likely a partition of my internal SSD), as is I am unable to use the internal drive for writing media files (like renders and when ingesting files.) Of note, I can "link" to files just fine, but importing to Avid codecs requires a drive the app can write to. When I launch the application without any external drives mounted, I get this warning: 



Per the Avid Knowledge Base a solution involves changing the write protection for the drive's root folder so as to allow Media Composer | First to create and populate its "Avid Media Files" folder: 


  Solution:
  
  If you do need to use the system drive as a media drive, take the following steps to change permissions
  
  
  Click on your system (Macintosh HD in most cases) drive to highlight
  From the File menu select Get Info (cmd+I)
  Click the lock icon in the bottom right to make changes
  Click on the “Read only” text in the Privilege column next to Everyone and set the privilege to “Read &amp; Write”
  You should now be able to see the system drive as a valid media drive.
  
  
  Note: If you repair permissions on the system drive, they will reset and you will have to repeat this procedure.


For whatever it is worth, I am the only user of this particular computer and I do have it backed up regularly with Time Machine. Partly I am asking for my own understanding, but also, if I were trying to set up a family member with this free editing software and they also let their kids use the laptop, it seems like granting everyone read/write might be make for more of a potential problem or accidents? Am I being overly cautious, or perhaps, by making the change, eagerly risky?
"Everyone" means all users, so yes, there is a risk, but only if someone already got into your system, and at that point they might already be brute-forcing your root password(when they've got it they're almost unstoppable). So as long as nothing bad gets into your system everything's fine and opening up your hard drive for everyone to edit doesn't rise the risk of that happening.