Was granting myself this permission a security risk?

Question

In a PowerShell script in Windows 10 Pro 64, I'm getting access-denied errors on several folders, such as:

• C:\Windows\System32\config\systemprofile\AppData\Local\Microsoft\Windows\INetCache\Content.IE5
• C:\Windows\System32\LogFiles\WMI\RtBackup

I went to look at those folders in File Explorer. I never did get into them, but along the way, on three folders:

• C:\Windows\System32\config
• C:\Windows\System32\config\systemprofile
• C:\Windows\System32\LogFiles\WMI

I got a message saying that I didn’t have permission to access them, but inviting me to click to get permission permanently. I clicked that. I’m now able to access those three folders like any other. In order to test what "permanently" meant, I rebooted. I'm still able to access those folders.

Three questions:

• Is it a security risk (or a bad idea for any other reason) to have those folders accessible? If so, how do I revert that permission?
• On the "RtBackup" folder, I got the same offer to give me permanent access, but when I clicked for that, the permission was denied and I was told that to get it I should go to the "Security" tab. Presumably that means of the folder properties. I'm thinking it might be a bad idea to mess around with security settings for a system folder. Is that right? What are the risks from doing that?
• In researching this, I came across the DOS command TakeOwn. I wonder if that might allow me to access all these elusive folders and maybe eliminate the access-denied errors in my PowerShell script. Would it? And would doing that be dangerous? What are the risks from running TakeOwn on an inaccessible folder?

Answer 1

File permissions are really designed for a multi-user system. If that's the case -- multiple people use this machine, or it's part of a corporate environment -- then giving yourself write permissions inside C:\Windows\System32\ means that you (or malware you download that's running as you) can muck things up for other users.

If this is a single-user system then the distinction between you and Admin is a bit less meaningful. As usual, there's a perfect XKCD for this:

XKCD comic "Authorization"

It's also worth noting that by giving yourself (and therefore any malware running as you) write permission to C:\Windows\System32\, you increase the chance that malware can escalate itself to being Admin, at which point it's easier for it to hide from any anti-virus software you might be running because now the malware is equally powerful as the AV.