web_xss_in_access_logs.yml

title: Cross Site Scripting Strings
id: 65354b83-a2ea-4ea6-8414-3ab38be0d409
status: test
description: Detects XSS attempts injected via GET requests in access logs
references:
    - https://github.com/payloadbox/xss-payload-list
    - https://portswigger.net/web-security/cross-site-scripting/contexts
author: Saw Win Naung, Nasreddine Bencherchali
date: 2021/08/15
modified: 2022/06/14
tags:
    - attack.initial_access
    - attack.t1189
logsource:
    category: webserver
detection:
    select_method:
        cs-method: 'GET'
    keywords:
        - '=<script>'
        - '=%3Cscript%3E'
        - '=%253Cscript%253E'
        - '<iframe '
        - '%3Ciframe '
        - '<svg '
        - '%3Csvg '
        - 'document.cookie'
        - 'document.domain'
        - ' onerror='
        - ' onresize='
        - ' onload="'
        - 'onmouseover='
        - '${alert'
        - 'javascript:alert'
        - 'javascript%3Aalert'
    filter:
        sc-status: 404
    condition: select_method and keywords and not filter
fields:
    - client_ip
    - vhost
    - url
    - response
falsepositives:
    - JavaScripts,CSS Files and PNG files
    - User searches in search boxes of the respective website
    - Internal vulnerability scanners can cause some serious FPs when used, if you experience a lot of FPs due to this think of adding more filters such as "User Agent" strings and more response codes
level: high