Learn English – Word/phrase for a feature that could be both good and bad for something

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Take this scenario:

a tool has a specific feature that could be regarded as an invaluable benefit for. However, this feature, if used in opposite direction may be counterproductive. In other words, the strength point may be the weakness point.

For example, feature X of a security mechanism could be leveraged to break that if used maliciously. So, what's the word/phrase to describe this feature? I think it should be something other than Achilles heel.

Best Answer

You could call this a double-edged sword. It can be used both for good and bad.