I work for Brave, a browser with ~80M users. We want to introduce a new system for automatic updates called Omaha 4 (O4). It's the same system that powers automatic updates in Chrome. O4 runs as a separate application on users' systems. For Chrome, this works as follows: An app called GoogleUpdater.app regularly checks for updates in the background. When a new version is found, then GoogleUpdater.app installs it into Chrome's installation directory /Applications/Google Chrome.app. But consider what this means: A separate application, GoogleUpdater.app, is able to modify Google Chrome.app. This is especially surprising because, for example, the built-in Terminal.app is not able to modify Google Chrome.app. Here's how you can check this for yourself: (Re-)install Chrome with its DMG installer. Run the following command in Terminal: mkdir /Applications/Google\ Chrome.app/test. This works. Undo the command: rm -rf /Applications/Google\ Chrome.app/test Start Chrome and close it again. mkdir /Applications/Google\ Chrome.app/test now fails with "Operation not permitted". (These steps assume that Terminal does not have Full Disk Access and System Integrity Protection is enabled.) In other words, once Chrome was started at least once, another application (Terminal in this case) is no longer allowed to modify it. But at the same time, GoogleUpdater.app is able to modify Chrome. It regularly applies updates to the browser. For each update, this process begins with an mkdir call similarly to the one shown above. How is this possible? What is it in macOS that lets GoogleUpdater.app modify Chrome, but not another app such as Terminal? Note that Terminal is not sandboxed. I've checked that it's not related to codesigning or notarization issues. In our case, the main application (Brave) and the updater (BraveUpdater) are signed and notarized with the same certificate and have equivalent requirements, entitlements and provisioning profiles as Chrome and GoogleUpdater. The error that shows up in the Console for the disallowed mkdir call is: kernel (Sandbox) System Policy: mkdir(8917) deny(1) file-write-create /Applications/Google Chrome.app/foo (It's a similar error when BraveUpdater tries to install a new version into /Applications/Brave Browser.app.) The error goes away when I disable System Integrity Protection. But of course, we cannot ask users to do that. Any help would be greatly appreciated.