I've tested this for two minutes so it must work without flaws 
Basically just changed uc_product_adjustments_form to store the serial data in 'value' instead of 'hidden'.
It seems to work without issue in my limited testing. I know it's a very small change, but it keeps the data from being sent or manipulated by the user.
-Shane
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| uc_attribute.diff | 339 bytes |