Mojave requires software update to access iphone, but doesn't give me any info as to what the update is

My newer iphone won't connect via lead to iMac running Mojave anymore (I need Mojave for older software I use). I get a message saying 'A software is required to connect to iPhone 13 xxxx. See screengrab

If I go to LEAN MORE button, I don't get any more information on what is being installed. I got cold feet pressing install, as it would be a disaster if it installed new OS over my current Mojave. Can anyone give me any info, will this just be a small update to Mojave to allow the iphone to connect to iMac? It wouldn't just install Catalina without telling me, would it?