Enemy attack bug

The Enemy Attack Bug in the NES version of Final Fantasy made status ailments inflicted by standard enemy attacks exempt from items intended to make characters immune to them.

For example, a Knight with an Aegis shield should be immune to Stone, but a Cockatrice can still still him to stone as a side-effect of its regular attack.

This bug made Mindflayers especially dangerous since their attacks had an instant death side-effect that the Protect Ring could not prevent.

This big was corrected in all subsequent ports and remakes of Final Fantasy.