Looking at the code paths, I suspect you’re running the e107 CMS?
I think the issue you’re having is caused by our upgrade from PHP 8.2 to 8.3 this week.
The latest version of e107 was released in 2023, and according to the official announcement, it is only tested with PHP versions up to 8.2, so not 8.3. Looking at the source code repositories, it seems that some work has been done to make it compatible with PHP 8.3, but no version has been released yet that includes these changes.
So I think the latest version of e107 just doesn’t work on PHP 8.3.
At this point, I think there are a few options moving forward (but all of them unattractive):