In a previous article we talked about the Alert key retirement plan, the retirement plan originally included releasing the private key to the public but this was only done recently. Any node running Bitcoin 0.12.x or more should have the alert system disable, while this is an ancient version of Bitcoin, about 4% of the current network is still vulnerable.
This made the Bitcoin Core developers create a final alert that overrides any previous alert and shows a warning message to all vulnerable nodes for wich an update is required. Unfortunately this didn’t turn out to be an optimal solution as this alert itself can be cancelled if another alert was to arrive at the node first. There were also fears that some Altcoins could still have the Alert system integrated into their code as a lot of them are just Bitcoin forks, upon further investigation it was found that only a small amount of altcoins on github are vulnerable, and almost all of them are abandoned anyway. Bitcoin developers also offered Altcoin developers a patch that can fix most issues regarding the Alert System, if they still wish to use it in their coins.