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I'm curious if Lockdown mode would prevent this exploit?

From Apple's Lockdown site, it's hard to tell the extent of what is locked down.

> Web browsing: Certain complex web technologies, like just-in-time (JIT) JavaScript compilation, are disabled unless the user excludes a trusted site from Lockdown Mode

This is allegedly the fix for this exploit for webkit: https://github.com/WebKit/WebKit/pull/3023, it appears to at least somewhat related to the JIT, but I don't know enough about the exploit, or webkit to make that determination.

"Processing maliciously crafted web content may lead to arbitrary code execution. An application may be able to execute arbitrary code with kernel privileges. Apple is aware of a report that this issue may have been actively exploited."

Sounds pretty serious, has active exploitation like this happened before in the Apple ecosystem or is this like most zerodays; edge cases and state level exploits that don't target broadly?

I have no hard data, but having looked at the security content of a lot of these over the years I'd wager WebKit has serious issues like this crop up more than any other component in iOS.

And the other advisories:

https://support.apple.com/en-us/HT213412

https://support.apple.com/en-us/HT213413