Fix one and add two.

There used to be a brilliant weather app here in Oz back in the early days of iOS. I always loved the update notes the author provided. One was "Fixed one grammatical error and introduced another one, can you find it?"

It depends on how good their testing practices and code review / auditing are. I want to believe they are some of the best in the industry, but that's making assumptions.

But jumping to assumptions that fixes introduce bugs is a bit rash and assumes incompetence / unprofessionality / unmonitored AI usage / kneejerk bugfix processes.

They don't introduce bugs. They introduce feature experiences.

I remember some research from IBM that showed that every two bug fixes introduced another bug. Effectively your queue for bugs is twice as long as you think.

No bugs, only intentional backdoors