There is hardly just one person responsible for doing this. There was at least one developer who implemented this solution, at least “designer” that can up with

There is hardly just one person responsible for doing this. There was at least one developer who implemented this solution, at least “designer” that can up with a solution for the initial problem, a dozen managers who oversaw that whole project, up to the minister who must have been aware of this problem. Let alone everybody who ever worked with this system and never reported that “bug”. So if you want to fire someone, start at the top for not overseeing this correctly or hiring the wrong person for the job and then work your way to the bottom. I believe it is much better to fix it (require a second authentication before sending those massages) and search for similar problems within the whole department to make sure something like this never happens again. Make sure everybody, including new hires, are aware of this incident, what the consequences were and that everybody is encouraged to report similar bugs and nobody has to be afraid to be fired when they make a mistake. Otherwise you just create an environment where everybody blames anybody but themselves and the “smallest” guy gets fired for mistakes other’s. This way, things get never fixed probably because everyone ist just afraid of the consequences.