This is more a question out of interest, not for a specific case. If there are regional differences regarding the answer, I am more interested in Central Europe (Germany) than elsewhere. I have not made such an error myself and obviously do not want to try. ;) Google turns up little.
As shown here https://www.cbsnews.com/news/stock-trade-typo-costs-firm-225m/ , there are cases where professionals cause a huge ruckus by mere (totally obvious) typos, causing millions of damage.
Now, these days, many consumer banks offer convenient online forms to do stock trading for everybody. Obviously, at least in the German banks I am familiar with, they strictly refuse any kind of liability against anything, and that the bank running the site just forwards the transaction orders to the exchange selected by the user.
I assume that all the usual "background noise" small transactions performed by "you and me" laymen are performed fully automated in the popuplar stock exchanges (NY, Frankfurt, ...) these days. Are there any known protections against obvious typos in the stock systems themselves? Do you know of stock exchanges which flags or rejects obviously wrong buy or sell orders (e.g., selling something for 0.1% of its highest buy order, or buying something at 1000 times the current sell order)? Does the stock exchange "community" have some sort of "rules of conduct" for this?