The document has > TOP SECRET [blackbox] NOFORN on it. That's crossed out and UNCLASSIFIED is inserted, but what's that black box covering up? Is it another level of secret access so secret we can't know the name?
On the basis of googling "top secret noforn filetype:pdf", it seems that the convention is for the redacted text to be some kind of source classification (eg. "SI" for Signals Intelligence or "COMINT" for Communication Interception. I have no idea what it would be in the case of this report, but my guess would be that it was redacted to avoid ambiguity given that "Unclassified" is stamped next to it, rather than beca…
Even vague descriptions of intelligence sources are often treated as more sensitive than the information derived from those sources.