MYBB captcha shows upper and lower case letters how come you enter lower case letters and it will be accepted? How to make it so that you will need to type exactly what captcha displays?
You'd have to edit the code, the reason it does it is to stop the issue with not knowing what case the letter is.
cC
yY
oO
pP
sS
jJ
kK
zZ
xX
vV
mM
if you imagine having a captcha of:
pCSxZ
You wouldn't have any idea what the cases of the letters are, so it will force it to lowercase and check that.