I see many topics argue about this, but none with an official rule or statement.

Stealth attachment from Imperial Black Ops stacks with the Hidden condition?

So if a group with the Stealth attachment attacked by a melee rebel, in the Precision count of the dices must have an 1+ Precision with a -2 Malus?

What's the source of the confusion?

The -2 Accuracy from Hidden is applied to the accuracy results regardless of attack type. Normally melee attacks ignore accuracy, so they are not affected by Hidden . With Stealth the accuracy in the attack pool during step 6 of the attack needs to be 1 or higher, or the attack misses .

There are a few melee weapons that guarantee 3 - 2 = 1 accuracy though (e.g. Vibrosword, Electrostaff). Shadow Armor could apply another -2 accuracy in addition to Hidden and make it harder to achieve the 1 accuracy.