0.1BTC were made out of thin air on Bitcoin Testnet on September 26. The attacker showed that it’s possible to exploit the inflation vulnerability bug. Reddit users called miners to help in defending the network.
Apparently, an attacker is mining the invalid-rules chain, the one built before they fixed the latest bug. They have exploited the Bitcoin Core’s bug CVE-2018-17144 to generate 0.1BTC on Testnet. See the exploit transaction and read more:
https://coinedtimes.com/bitcoin-testnet-under-attack/ Wow, I didn't know that such serious bugs could be found. I mean, consensus protocol is one of the most important things about a cryptocurrency, so a flaw in it shakes the trust. 0.1 btc is not that much and it's good that it was noticed rather fast, but it makes me wonder whether there could be similar cases in which the bug just wasn't noticed and is still not, so some people are 'making btc' in bug amounts just now
It's just that the impossibility of invalid transactions to get confirmed is one of the strongest points about cryptocurrencies. They can't be faked. Or can they?