Tightlipped in a sentence as an adjective

For good or bad, MS is being tightlipped about a lot of things these days, and taking speculation for granted hits the credibility of the article writers.

Tightlipped definitions

adjective

inclined to secrecy or reticence about divulging information; "although they knew her whereabouts her friends kept close about it"

See also: close closelipped closemouthed secretive