Every one of them has vulnerabilities that a knowledgeable thief could theoretically exploit.
2016年12月四級真題（第一套）閱讀 Section B
柯林斯高階英漢雙解學習詞典釋義
ADV
從理論上說;照理說
You use theoretically to say that although something is supposed to be true or to happen in the way stated, it may not in fact be true or happen in that way.