InDesign CS5 is very old, is no longer supported, and doesn't work in macOS 10.2.6.
And I have never heard of installing updates using Terminal.
You're on your own!
Thanks for your answer Steve. Sadly I don't have the resources to buy a newer version and would hope to still be able to use such an expensive product.
I found a document instructing how to install using a Terminal window to get around the MacOSX Gatekeeper restrictions - it works well.
could you share those instructions? i haven't come across that before.
even with it working otherwise normally though, UI bugs like this seem to crop up a lot with people running newer mac OS versions with adobe CS apps. it might be something you'll have to live with.
You open the installer using Show package contents (right click or Ctl click), navigate to Mac folder and there is a file in there. Drag it into an open Terminal window, then press return in the Terminal window. The installer then launches and MAC OSX asks you for your password
If you have an older Mac, you have the option of restoring the original OS. I had a similar issue in the past and I partitioned my hard drive with a copy of the older OS, so I had the option to boot in the older or newer OS, as needed. If you choose to do this, be sure to back up everything first.