Stupidity is malice when you are supposed to be competent.

I.e. if a politician puts a first aid kit on some wounded person in the wrong way, it is not malice, but if a doctor can't do it properly, it is.

How Mozilla treats us Firefox lusers is malice. E.g. silently enabling spying via updates, pushing disruptive UI changes, or what not.

Mozilla might have been the doctor at one point but now they’ve morphed into the politician. The Google gravy train has utterly destroyed Mozilla’s ability to innovate. The whole culture over there has become completely corrupt and self-indulgent and the good ones have either left or been let go. Sad days.

Sufficiently advanced malice is indistinguishable from stupidity.

Good point :-)

But I think it is more common and makes more sense too to put it the other way around:

Any sufficiently advanced stupidity/incompetence is indistinguishable from malice.

It is as correct to say that sufficiently advanced stupidity is indistinguishable from malice. The difference between these claims and Hanlon's Razor is that the razor warns against assuming the malice in the absence of evidence.

It’s plausible deniability