There's a few reasons, the most obvious being that everyone uses them and gets them fixed. The less obvious is that it gives Blizzard an insight in to how much we can actually exploit, and work out what vectors are used; a lot of the public ones unfrtouantely pale before private ones.
Yeah, this. Essentially it is like an efficient market. Truly valuable exploits are fixed instantaneously. Publication means they no longer exist. No one benefits from that.
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