Do Firefox/IE add-ons have the same vulnerabilities?
Not so far, from what I read at the ars technica site. Only Chrome. However, that may simply mean that none has yet been discovered on the other browsers so I thought this important enough to make others aware and begin checking their own extensions for possible similarities.
Actually, Firefox may be at risk. Extensions, by their very nature, use Chrome as an executable mechanism. If you ever go to configure one of your extension in Firefox, for instance, you may notice the URL line starts with chrome:\\
Better safe than sorry.