You find a web application that uses the following query structure to authenticate users: "SELECT $*$ FROM userstable WHERE username $=$ "userinput$1"$ and password $=$ "userinput$2"$;$"$ You replace userinput $1$ with $\text{'}$OR $1=1\text{'}$; which gives you access to the database without having to enter a user name or password as $"1=1"$ is always true and the rest of the query is ignored. What computer fraud and abuse technique is this?

a$.$ zero$-$day attack

b$.$ URL hijacking attack

c$.$ SQL injection

d$.$ buffer overflow attack

e$.$ web page spoofing