I don't have it in front of me, but I'm talking about the "nobody but us" era of exploit markets:
https://en.wikipedia.org/wiki/NOBUS
Where the NSA seemingly was buying anything, even if not worthwhile, as a form of "munitions collection" to be used for the future attacks.
edit: this mostly ended in the US because other nations started paying more, add in more regulations (only a handful companies are allowed to sell these exploits internationally) and software companies starting to do basic security practices (along with ruling out their own bug bounties), it just mostly whimpered away.
Also relevant to the discussion, the book discusses how the public exploit markets are exploitive to the workers themselves (low payouts when state actors would pay more) and there are periods of times where there would be open revolts too (see 2009 "No More Free Bugs" movement, also discussed in the book).
Definitely worth it if you aren't aware of this history, I wasn't.
In reality, intelligence agencies today don't even really stockpile mobile platform RCE. The economics and logistics are counterintuitive. Most of the money is made on the "backend", in support/update costs, paid in tranches; CNE vendors have to work hard to keep up with the platforms even when their bugs aren't getting burned. We interviewed Mark Dowd about this last year for the SCW podcast.
Kid was simply born in the wrong era to cash out easy money.
Building reliable exploits is very difficult today, but the sums a reliable exploit on a mainstream mobile platform garner are also very high. Arguably, today is the best time to be doing that kind of work, if you have the talent.
The biggest problem, again, is that the vulnerabilities disappear instantaneously when the vendors learn about them; in fact, they disappear in epsilon time once the vulnerabilities are used, which is not how e.g. a mobile browser drive-by works.
It's only because the researcher contacted them.
discovered: they audited or pentested themself and found out, preemptively
I just mean that Coinbase didn’t see anything happening and didn’t take action though the boy successfully exploited the vulnerability on their live system.
I'm not talking about XSS specifically, I mean in general. An XSS isn't usually high-value, but if it affects the right target, it can be very valuable. Imagine an XSS or CSRF vuln in a web interface for firmware for industrial controls used by an enemy state, or a corporation in that state. It might only take 2 or 3 vectors to get to that point and then you have remote control of critical infrastructure.
Oh - and the idea that a vendor will always patch a hole when they find it? Not completely true. I have seen very suspicious things going on at high value vendors (w/their products), and asked questions, and nobody did anything. In my experience, management/devs are often quite willing to ignore potential compromise just to keep focusing on the quarterly goals.
I'm not saying they stockpile vulns; I'm saying if somebody on the dark web said they had a vuln for sale for $50k, and it could help an agency penetrate China/Iran strategically, it would make no sense to turn it down, when they already pay many times more money to try to develop similar vulns.