PHP Fatal Error after switching to PHP 8

I have a ModX website with version 2.7.2-pl.

After updating to PHP 8, I get the following error:
PHP Fatal error: Unparenthesized a ? b : c ? d : e is not supported. Use either (a ? b : c) ? d : e or a ? b : (c ? d : e) in /core/model/modx/modx.class.php on line 678

Is there a ModX update available which provides PHP 8 compatibility?
How do I update the ModX website? I am new to ModX and took over managing the website from someone else.

Please upgrade to version 2.8.4, the current version of the 2.x branch.

The simplest way is to use the extra UpgradeMODX.

Please make sure to backup your site (files and database) before the upgrade, in case anything breaks during the process.

Thank you for your reply. I saw that UpgradeMODX has already been installed. Where exactly do I find the upgrade option? Could you please provide a screenshot?

There should be a widget right on the start page of the MODX manager with an “Begin Upgrade” button. (You may have to scroll down inside the widget to see the button.)

If you don’t see the widget, go to “Cogwheel Icon” → “Dashboards” and add the widget “Upgrade MODX” to the active dashboard.

FYI, If you are not a member of the Administrator group, you won’t be able to use UpgradeMODX or see it on the Dashboard unless the ugm_groups System Setting has been changed to include a user group you belong to.