WordPress 4.5 is out, and as ever you ought to keep your WordPress website up to date with the latest security updates. However…WordPress 4.5 installs the latest version of a library called jQuery – that’s their policy, to keep up with the latest updates. Unfortunately the developers of jQuery seem to have lost their marbles and in the latest version they have fixed a ‘bug’ that allowed developers to pass parameters to a certain function call without quote marks (so,technically wrong). Unfortunately many plugin/theme developers have coded that way (probably millions of websites use this) and so fixing the “bug” breaks a whole lot of code!
So I’d give this update a long pause to allow developers to fix their plugins and themes, before applying the latest WordPress update. Keep backups as ever, and check carefully for errors after you’ve updated. The kind of issues you can expect are dynamic effects; accordions, tabs etc. not working – not the entire website not working – so you have to look quite hard to spot issues.
I’m sure the jQuery developers have some reasoning behind this total madness other than just “it just isn’t right” to justify them breaking many many websites; although having worked with developers all my life it wouldn’t surprise me if it was. And shame on the WordPress folks to let this slip through and pass the buck without realising that many people rely on third parties to deliver their WordPress functionality and will be in the hands of those third parties to make appropriate updates. WordPress 4.5 – not the greatest WordPress release I’m afraid.