You are a senior programmer at a Fortune $1000$ company. A junior programmer has been redesigning a web form where investors will submit a request for stock purchase. Your junior colleague has asked you to look at their code for a text box. You notice the the user input is being validated using a regular expression.

This method will add complexity to the code and could lead to a zero$-$day exploit

This is considered a good programming practice

This is unnecessarily complex and will increase the cost of the final product

Regular expressions are not intended for this type of use