Exploiting obvious errors of the game: A bug is an obvious error of Tibia or any other part of CipSoft's services, which is surely not intended to be that way - for example if the fire wave of dragons would suddenly heal you instead of damaging you, or if an NPC sells a certain rune for a much lower price than all other NPCs. If you abuse any obvious game error, e.g. by buying hundreds of backpacks of these cheap runes, your account will be most likely punished for it. Note that already a statement in which you admit that you have abused an obvious error may lead to a punishment.
Exploiting obvious errors of any other part of CipSoft's services: Also possible errors that might appear outside of the game may not be exploited, e.g. if there is a bug that allows you to manipulate the website in a way that you can transfer a character to another game world although it has a black skull, you are not allowed to abuse this error. CipSoft's services include among others all of CipSoft's other products and its websites. Therefore also a statement like "Yesterday I duplicated items in TibiaME by using this cool bug." may lead to a punishment.