This is not a "concern", this is literally what happens. Even prior to AI vulnerability scanning, release notes and diffs for any normal release or security patch of popular software were analysed and used to develop exploits, which could then be applied against non-upgraded instances. Nowadays, AI is doing this en masse and automatically producing exploits. And, as has been demonstrated, nowadays even the rumour of a major security bug is enough for people to find it, as people will immediately burn huge volumes of tokens looking for it.
Nor can you just keep it quiet and smuggle it out in a regular release as you suggest. For one thing, changes in important software are be linked to commits and have pull requests, reviews, etc. Changes without these will immediately raise suspicion, as either a malicious change snuck into a release, or as a "quiet" fix to a major vulnerability, completely undermining the purpose of keeping it quiet in the first place. Moreover, major vulnerability fixes cannot be "quiet", because the whole point is to get as many people as possible to upgrade as quickly as possible. If PHP (or whoever) push out a release containing a major security fix, but don't make this clear, then many people will be in no rush to upgrade, and will get pwned.
> This is not a "concern", this is literally what happens.
Sorry, I should have been specific: the concern is that this will happen faster than even the more fastidious admins (or daily or even hourly automated checks) will spot and apply updates.
> nowadays even the rumour
I think a lot fewer people would have paid attention at all without the rumour. Some ne'er-do-wells might have scanned a larger update for security issues otherwise, but I suspect most of those spending tokens on PHP this week would not have bothered had there just been a standard maintenance release that may or may not have included changes for a security issue that may (but probably not) have been so globally significant.
That is, at least in part, why the question of how to manage the release of updates like this is not a settled debate.
> then many people will be in no rush to upgrade, and will get pwned.
The worst case that we may be heading towards is that for any services on public facing infrastructure we might have to automatically apply updates with little or no time to verify, just to try be ahead of the ne'er-do-wells, with even superficial updates not mentioning the changes until a short time after to avoid giving clues to those who will scan for security issues if any such is mentioned (or nothing is mentioned - saying nothing about a security-only update only works if you say nothing about all updates, and you don't want to hold off on security-only updates on a slow moving project that might not have a non-security patch for quite some time).