Meanings of hidden weaknesses in English

He put Strang through his whole repertoire of physical feats, searching him the while for hidden weaknesses.

There are dozens of scanner programs on the Internet, which make it possible to stalk the Web for hidden weaknesses.

Each airplane must be overhauled after a few hours of flight to discover hidden weaknesses and to tighten sagging wires.

The steady and pitiless march of the hidden weaknesses in our constitutions, through illness to death, is painfully revealed by these histories of twins.