How can we know if something is bugged is if something is out of the ordinary or too good to be true. However, if we didn't know it was a bug talking about an obvious error could possibly lead to punishment.
An example of a bug that we had know idea really if it was a bug or not during Winterlight Solstice event 2020 some mini bosses like Cobra were still effected by the rapid respawn bonus, and we knew that supposedly Cipsoft didn't want mini bosses or bosses effect by this so we brought it to their attention and their planning to fix it by next Winterlight Solstice event.
Sometimes Cipsoft doesn't know there's bugs until we bring it to their attention. I think if you find a bug or something that doesn't seem right maybe it's a good idea to tell Cipsoft before your friends in this case.
I've heard a story of players getting punished in other ways. Like once apparently there was a house bug where 2 or 3 players could get a house on a new server and not any others. So when the players got their houses they sold potions from casks and made a huge amount of profit and got tons of Tibia Coins as a result. Because of this Cipsoft didn't reset the server but removed all the Tibia Coins and Items bought during that period instead. A lot of people were reportedly upset because no one knew it was a bug but they still got punished as a result. Please see the source for more details:
I'm going to tell you exactly what is considered bug abuse by pasting a part of the Tibia Rules below so you get a better understanding:
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.
Rule 3a) Bug Abuse
Exploiting obvious errors of the game or any other part of CipSoft's services.