It typically opens the default browser regardless of which browser you're actually using. I'm wondering if there's a funky registry key or something that confuses things for your system.
Either way, we usually launch the default system browse, which is not necessarily the browser you started the installation with. This is a long-standing bad experience, and something that I complain to the team that makes the installer about on a regular basis. Everyone involved recognizes that the behavior is less than ideal, but it's a fundamental design problem and it's not something that can be addressed with a simple fix. It *is* very much on the radar as something that we want changed, and I'm pretty sure that it will get resolved in the installer over the long-term.
In the meantime, if you would like to avoid the Flash Player upgrade process entirely, Google Chrome includes Flash Player as a built-in component. There's nothing separate to download from Adobe, and all the updates are made available directly through Chrome's update mechanism.
I'm curious - how does the Flash installer determine what is the default system browser under Windows 7?
The two registry keys I'm aware of which can be used are:
...and on my system both these keys are set to the correct browser (not IE).
I too just updated Flash on a Windows 7 machine and it pulled the same stunt - launched Internet Explorer instead of the default browser.
Can't say I was impressed by the suggestion above, to switch to Chrome.......!