After High Sierra Update all files report "damaged and can't be opened"

I found this link that fixed the issue properly.

https://macperformanceguide.com/blog/2017/20171124_1510-macOS-HighSierra-AppleCo reRot.html

The key command is below. Open Terminal and cd to the directory containing your "Damaged files"

xattr -d com.apple.quarantine *.pdf *.dmg

This fixed all my issues

Yea ... running 10.13.3, done migration from mbp 2013 to a mbp 2015 have same issue . Fixed by disabling gatekeeper, hope a later update fixes this because it's counter productive to do a migration and it corrupting/mistrusting your apple signed files ...

1. Backup old Mac fully to Time Machine disk

2. On the new Mac hold Cmd+R to boot from Recovery

3. Choose Restore from Time Machine backup and choose the disk from step 1

4. Let the system do its thing, it should then bootup and be useable.

This issue seems to occur due to Migration Assistant doing a shoddy job of converting HFS+ to APFS on the fly.

Can anyone else confirm this solution?

Thank you

I ran into the same problem after using the Migration Assistant to move files from an iMac 2015 running Sierra to a new iMac 2017 running High Sierra (10.13.3). I couldn't open any file that was downloaded from the Internet including .pdfs nor files from email attachments, or even files I copied on to the machine post migration. While the previously referenced gatekeeper fix did work, it's not something I wanted to rely on because of the increased risk. I spent quite a bit of time with Apple Care changing permissions on the file system, etc.; it didn't work. Also the problem impacted all users on the system including a new user created after the migration. Finally, I reinstalled the OS and that seems to have fixed everything.

Can confirm this fixed my issue.

Used migration tool to move from 2013 13" Macbook Pro Retina to New 2017 Macbook Pro 15.4" and files were all damaged etc. Actually got the error when after dowloaded the newest Parallels, tries to install and it said the same thing, I was worried but thanks for this advice!

I had the same problem after using migration assistant to move my files over to a new iMac from a 2012 iMac. The behavior was unusual. for example, I could open an .jpg in Preview once, but if I tried to view it immediately afterward a second time I got the damaged file message. I tried resetting permissions using the terminal in utilities with no result. Finally after spending a few hours on the phone with Apple support they concluded that the operating system on my new iMac must be damaged. After reloading the operating system, the problem was solved. Apple support did a wonderful job of patiently working with me to solve the issue.

Check this discussion on StackExchange: sierra - Gatekeeper preventing from opening files from Finder (launching apps is fine) - Ask Different

I had the same issue, the above fixed it. The file /var/db/gkopaque.bundle was damaged (zero bytes) which was the root of the issue. Replacing this file with a known good copy completely eliminated the "damaged file" message.

This works WITHOUT disabling Gatekeeper, which from a security perspective is a much better solution for everyone.

I have reported this fix to Apple Support so hopefully word gets out there. It took me a long time to track this down, and I'm really thankful to the person on StackExchange who was persistent enough to keep digging until a solution was found.

I did the same exact thing as you have described and have the same problem. On hold w Applecare now. This is beyond frustrating.

I can confirm that this fix works!!

Hopefully Apple will fix this soon so we can get back to having just the checkbox for opening apps from Apple Store and known developers checked.

I just found that I can no longer update IntelliJ IDEA or its plugins. It cannot access the files for update. This app isn't bought through the app store.

Fixed for me in 10.13.2

Seems fixed for me too, but not sure what exactly caused the problem. Didn't see anything relevant in the release notes.

Even better to change e.g all files in Documents folder

xattr -rd com.apple.quarantine ~/Documents

/Rob

At least there was a simple fix - reinstalling your whole d-m machine

Had to do the same thing and i downgraded to Sierra ...