The Web Application Hacker’s Handbook Discovering and Exploiting Security Flaws

Try supplying a simple mathematical expression that is equivalent to the

original numeric value. For example, if the original value was 2, try sub-

mitting 1+1 or 3-1. If the application responds in the same way, then it

may

be vulnerable.

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The preceding test is most reliable in cases where you have confirmed

that the item being modified has a noticeable effect on the application’s

behavior. For example, if the application uses a numeric 

PageID

parame-

ter to specify which content should be returned, then substituting 1+1 for

2 with equivalent results is a good sign that SQL injection is present. If,

however, you can place completely arbitrary input into a numeric para-

meter without changing the application’s behavior, then the preceding