I got a notification that there is a Netflix app update available. When I click on the Update button, it asks me to confirm my credit card info and then asks me to confirm that I want to buy the item.
Is this normal? Shouldn't an update be free?
What kind of notification did you get? AFAIK the only way to know if an app update is available is through the App Store app via "Updates". When the app is open it will display a number next to the "Updates" icon (circled down arrow, lower RH corner) indicating that one or more apps have an update available . Tap on the "Update" icon and a list of app(s) will appear that need updating. Tap on "Update" or "Update All" in the upper RH corner and you will be prompted for your Apple ID. Enter your ID and the updates will begin downloading and installing.
If the notification you received is anything other than that...an email for example, it's almost certainly spam and s/b deleted (or bounced in your regular mail program) immediately.
Others may chime in but I hope that helps, thanks for posting and we'd welcome any more details. It's always good to know about these things.
EDIT: Posted before I saw Keeep's response...great minds think alike.