Friend very good question,I Can give answer for this,
for example the is a square function(object)like below
   f(x)=x*x; x is defined such that x!=any negative value.
for example
 if you supply x=2 then answer is 4,
 in same case if you supply x=-2 then the answer is also 4

if the function is square then it can take both positive 
and negative values Both.

Here the condition enforecement failure,there is some code 
missed for frontend or backend(database).
here the functionality is workingbut taking additional 
values.
so we need to provide input constraints to take inputs.
this can be reported as medium Severity defect to the 
development people.
  
if you have any doubt plz mail me without any hasitation
i am open for clearing.

mail me at: rajendra_penumalli@yahoo.com
callme at :9885162742(AP cell number)

thanks rajendra its a very good answer
                                         maheswar