Unless I missed something, those articles just give specific examples of agents being uncovered. Nothing is given to indicate how many remained uncovered. Its a pretty long jump from examples of such to the general statement that "the majority of official-status officers" being known by their host countries.
>"United States counterintelligence specialists estimate that at least 150 K.G.B. officers are working out of the embassy under cover as diplomats, clerks, chauffeurs, journalists and in other jobs."
Just as a point of reference, the US Embassy in Iran during the 1979 revolution and subsequent hostage crisis had something on the order of 75-100 people working there.
Again, Google around, there is a ton of material out there on these topics. If you read Russian, I'm sure there are similar stories talking about US spies. (Although the reliability of Soviet media is questionable at best) I was really interested in this stuff when I was a kid, and recalled these events vaguely from those days, there's plenty more to find.
What evidence would you like? Embassy payroll documents annotated with "spy" and "not a spy"?
Given the privileged status of the embassy and the protections offered by diplomatic status (eg the diplomatic pouch) you'd be crazy not to staff your embassy with spies, at least in any country worth spying on. You'll probably get a few actual diplomats to do the actual diplomacy too, and the occasional low-level passport stamper, but the default assumption should be that they're pretty much all spies.
My point is that this is the kind of evidence you would need to support the original claim. If the top-level comment I was pursuing had, instead of making the claim that the majority of the spies posing as diplomats were known as spies to the host nation, had rather claimed that many of them were known, I wouldn't have pursued it.
I think you need to read this comment thread starting at the top: my point is that the original claim I was asking for a citation in is essentially unsupportable, so no citations exist.
