If a device is jailbroken / rooted, it means that the user has full system access / control.
Because of that level of control some apps won't run or won't allow full functionality because they consider that the devices security is compromised.
There is no definitive way to detect if a device is rooted. Its typically done by checking for the existence of specific apps/libraries and/or the ability to perform certain actions and/or read/change specific settings.
A normal app/OS update is not going to give you root access, so it seems that the optus app has made a false positive, which means its a bug with the optus app.
Do you get the error message after logging or before you are even asked to log in?
I get it as soon as I open any optus app. Screen says along the lines of "warning this divice is rooted/jailbroken could cause harm and optus protects customer details ect " only option I get is EXIT in yellow box at the bottom
That was useful info, thanks .
Not sure what is going on there, Topaz7.
A similar issue was experienced for some users with the Optus Sport app last year.
This thread contains some info and a link to report a fault so I would suggest giving that a try as it was eventually fixed.