Sounds like Jagex is trying to prevent players using unofficial RuneScape Clients like Swiftkit. 
I'm guessing this is the RuneScape Downloadable Client we were promised?
The downloadable client has been available for a number of years, i believe they said something about updating it to support things like "the Runescape game bar". I'm assuming this is the first step in this though.
Sad no Chrome support though

. Then again, Chrome doesn't have many 'attachments' does it?