EDIT: "Last week, Prime Minister Benjamin Netanyahu called on Likud supporters to download the application in order to help draft more supporters and voters."
Having said that - we need to differentiate between the intended use of the "Elector" app, which is individual record search, and the ability to obtain all records. The latter is due to a bug, and that's the leak. As for the former, I'm not sure exactly about its legality in the first place; perhaps others can comment on this.
Personally I would have said that is normal, legitimate processing; and any definition of "data leak" that included that would be so broad as to be meaningless.
Of course, the leak of the full register by a negligently designed website is another matter...