Either pronunciation is acceptable - both with and without the 'st' pronounced. It's really not worth worrying about. There are many more important and interesting things to focus on in the English language.

The "st" IS pronounced. There's no reason for it to be silent. Even a google search will show the "st" is pronounced. You can also check on youtube, forvo.com and howjsay.com.

Thank you :)

It is pronounced, but even if one didn't pronounce it that way it is usually heard that way because the word, "unbeknownst" is almost always followed by "to me", or "to her".. so the "t" in "to" creates the sound of "st" in "unbeknownst". Hope that makes sense.

Have you been banned on Google? :D and the answer is NO, 'st' is not pronounced