First, make sure you have root access enabled. From the home screen, go to Apps, scroll down to Settings, and open it. In Settings, the next-to-last option should be Developer Options. If it isn't there, select the last option, About Media Box, then scroll down to the last item at the bottom, Build Number, and click it repeatedly until it says "You are now a developer." Then press Exit, and Developer Options should be visible. Now click on Developer Options, scroll down to Root Access (it's just above the "Debugging" heading). If it's off, click it to turn it on.
While you're in Settings, you also need to scroll to the Personal section, click on Security, scroll down to Device Administration, and make sure Unknown Sources is turned on, so you can "side-load" apps from sources other than the Play Store.
The next thing you need is a file manager that can access the filesystem's root. The CyberBox comes with FileBrowser, but that only accesses the Cyberbox's internal and external (USB) storage areas. So I used a file manager called MiX (short for Mix of eXplorers): https://forum.xda-developers.com/att...7&d=1580815875
. You can browse to this AVSForum post with Chrome 66 (the same Chrome 66 you want to remove) and click on that link. It should download MiX and offer to install it. Go ahead and install and open it.
MiX is a bit counter-intuitive until you get used to it, and it's easiest to use with a mouse, so if your CyberBox remote isn't in mouse mode, click "TV" to switch to mouse mode. Now use the mouse to click the "hamburger" (three stacked horizontal lines) at the top left of the MiXplorer menu. Then click Root (it should be the third or fourth item in the menu that drops down).
Chrome is in the /system/app directory, so scroll down to the "system" folder. Don't click the icon; click the name. (If you accidentally click the icon it will select the folder; just press Exit to deselect it.) Then click on "app" too. Now you'll see subfolders for all your "system" (non-removable) apps, including Chrome. (There's also a "ChromeCustomizations," but I don't know what that is, so I just left it alone.) We're going to make a backup copy of the Chrome folder, then delete it.
Select the Chrome folder by either clicking its icon, or clicking the name but holding the OK button down for a few seconds. The icons at the top right will change. The second one, which looks like two overlapping windows, is the "copy" icon. Click it and MiX will respond "Added to the task list." Now press Exit on the remote until you get back to root; then press exit twice more. This should bring you back to Internal Storage.
If you wish, at this point you can click the "hamburger" again and select your USB drive, instead of Internal Storage, as the place to save your copy. But either way, click the Paste icon (it looks like a clipboard). MiX will ask for confirmation by saying Copy #1
not started. Click that and it will copy your folder. Now you can navigate back to Root / system / app, select Chrome again, and click the trash can to delete it, and confirm you really want to delete it. Finally, reboot the CyberBox by holding down the power button until the menu comes up and selecting Restart. Once it reboots, Chrome 66 should be gone, so you can install the latest version from the Play Store. (But if anything goes wrong, you can bail out by copying the Chrome folder back to /system/app.)
Q: Why didn't we just "cut" the Chrome folder, rather than copying it and then deleting it? A: The folders are in different partitions (like different drive letters on Windows) and MiX will only cut & paste within a single partition, so we had to do it the hard way.