DAST browser-based analyzer

Version history
Do not run DAST scans against a production server. Not only can it perform any function that a user can, such as clicking buttons or submitting forms, but it may also trigger bugs, leading to modification or loss of production data. Only run DAST scans against a test server.

The DAST browser-based analyzer was built by GitLab to scan modern-day web applications for vulnerabilities. Scans run in a browser to optimize testing applications heavily dependent on JavaScript, such as single-page applications. See how DAST scans an application for more information.

To add the analyzer to your CI/CD pipeline, see getting started.

How DAST scans an application

A scan performs the following steps:

  1. Authenticate, if configured.
  2. Crawl the target application to discover the surface area of the application by performing user actions such as following links, clicking buttons, and filling out forms.
  3. Passive scan to search for vulnerabilities in HTTP messages and pages discovered while crawling.
  4. Active scan to search for vulnerabilities by injecting payloads into HTTP requests recorded during the crawl phase.

Crawling an application

A “navigation” is an action a user might take on a page, such as clicking buttons, clicking anchor links, opening menu items, or filling out forms. A “navigation path” is a sequence of navigation actions representing how a user might traverse an application. DAST discovers the surface area of an application by crawling pages and content and identifying navigation paths.

Crawling is initialized with a navigation path containing one navigation that loads the target application URL in a specially-instrumented Chromium browser. DAST then crawls navigation paths until all have been crawled.

To crawl a navigation path, DAST opens a browser window and instructs it to perform all the navigation actions in the navigation path. When the browser has finished loading the result of the final action, DAST inspects the page for actions a user might take, creates a new navigation for each found, and adds them to the navigation path to form new navigation paths. For example:

  • DAST processes navigation path LoadURL[https://example.com].
  • DAST finds two user actions, LeftClick[class=menu] and LeftClick[id=users].
  • DAST creates two new navigation paths, LoadURL[https://example.com] -> LeftClick[class=menu] and LoadURL[https://example.com] -> LeftClick[id=users].
  • Crawling begins on the two new navigation paths.

It’s common for an HTML element to exist in multiple places in an application, such as a menu visible on every page. Duplicate elements can cause crawlers to crawl the same pages again or become stuck in a loop. DAST uses an element uniqueness calculation based on HTML attributes to discard new navigation actions it has previously crawled.

Passive scans

Passive scans check for vulnerabilities in the pages discovered during the crawl phase of the scan. Passive scans are enabled by default.

The checks search HTTP messages, cookies, storage events, console events, and DOM for vulnerabilities. Examples of passive checks include searching for exposed credit cards, exposed secret tokens, missing content security policies, and redirection to untrusted locations.

See checks for more information about individual checks.

Active scans

Active scans check for vulnerabilities by injecting attack payloads into HTTP requests recorded during the crawl phase of the scan. Active scans are disabled by default due to the nature of their probing attacks.

DAST analyzes each recorded HTTP request for injection locations, such as query values, header values, cookie values, form posts, and JSON string values. Attack payloads are injected into the injection location, forming a new request. DAST sends the request to the target application and uses the HTTP response to determine attack success.

Active scans run two types of active check:

  • A match response attack analyzes the response content to determine attack success. For example, if an attack attempts to read the system password file, a finding is created when the response body contains evidence of the password file.
  • A timing attack uses the response time to determine attack success. For example, if an attack attempts to force the target application to sleep, a finding is created when the application takes longer to respond than the sleep time. Timing attacks are repeated multiple times with different attack payloads to minimize false positives.

A simplified timing attack works as follows:

  1. The crawl phase records the HTTP request https://example.com?search=people.
  2. DAST analyzes the URL and finds a URL parameter injection location https://example.com?search=[INJECT].
  3. The active check defines a payload, sleep 10, that attempts to get a Linux host to sleep.
  4. DAST send a new HTTP request to the target application with the injected payload https://example.com?search=sleep%2010.
  5. The target application is vulnerable if it executes the query parameter value as a system command without validation, for example, system(params[:search])
  6. DAST creates a finding if the response time takes longer than 10 seconds.

Getting started

To run a DAST scan:

Create a DAST CI/CD job

  • This template was updated to DAST_VERSION: 2 in GitLab 14.0.
  • This template was updated to DAST_VERSION: 3 in GitLab 15.0.

To add DAST scanning to your application, use the DAST job defined in the GitLab DAST CI/CD template file. Updates to the template are provided with GitLab upgrades, allowing you to benefit from any improvements and additions.

To create the CI/CD job:

  1. Include the appropriate CI/CD template:

    The latest version of the template may include breaking changes. Use the stable template unless you need a feature provided only in the latest template.

    For more information about template versioning, see the CI/CD documentation.

  2. Add a dast stage to your GitLab CI/CD stages configuration.

  3. Define the URL to be scanned by DAST by using one of these methods:

    • Set the DAST_WEBSITE CI/CD variable. If set, this value takes precedence.

    • Adding the URL in an environment_url.txt file at your project’s root is great for testing in dynamic environments. To run DAST against an application dynamically created during a GitLab CI/CD pipeline, write the application URL to an environment_url.txt file. DAST automatically reads the URL to find the scan target.

      You can see an example of this in our Auto DevOps CI YAML.

  4. Set the DAST_BROWSER_SCAN CI/CD variable to "true".

For example:

  - build
  - test
  - deploy
  - dast

  - template: DAST.gitlab-ci.yml

    DAST_WEBSITE: "https://example.com"


The browser-based analyzer can authenticate a user prior to a scan. See Authentication for configuration instructions.

Available CI/CD variables

These CI/CD variables are specific to the browser-based DAST analyzer. They can be used to customize the behavior of DAST to your requirements. For authentication CI/CD variables, see Authentication.

CI/CD variable Type Example Description  
DAST_ADVERTISE_SCAN boolean true Set to true to add a Via header to every request sent, advertising that the request was sent as part of a GitLab DAST scan. Introduced in GitLab 14.1.  
DAST_BROWSER_ACTION_STABILITY_TIMEOUT Duration string 800ms The maximum amount of time to wait for a browser to consider a page loaded and ready for analysis after completing an action.  
DAST_BROWSER_ACTION_TIMEOUT Duration string 7s The maximum amount of time to wait for a browser to complete an action.  
DAST_BROWSER_ALLOWED_HOSTS List of strings site.com,another.com Hostnames included in this variable are considered in scope when crawled. By default the DAST_WEBSITE hostname is included in the allowed hosts list. Headers set using DAST_REQUEST_HEADERS are added to every request made to these hostnames.  
DAST_BROWSER_COOKIES dictionary abtesting_group:3,region:locked A cookie name and value to be added to every request.  
DAST_BROWSER_CRAWL_GRAPH boolean true Set to true to generate an SVG graph of navigation paths visited during crawl phase of the scan.  
DAST_BROWSER_DEVTOOLS_LOG string Default:messageAndBody,truncate:2000 Set to log protocol messages between DAST and the Chromium browser.  
DAST_BROWSER_ELEMENT_TIMEOUT Duration string 600ms The maximum amount of time to wait for an element before determining it is ready for analysis.  
DAST_BROWSER_EXCLUDED_ELEMENTS selector a[href='2.html'],css:.no-follow Comma-separated list of selectors that are ignored when scanning.  
DAST_BROWSER_EXCLUDED_HOSTS List of strings site.com,another.com Hostnames included in this variable are considered excluded and connections are forcibly dropped.  
DAST_BROWSER_EXTRACT_ELEMENT_TIMEOUT Duration string 5s The maximum amount of time to allow the browser to extract newly found elements or navigations.  
DAST_BROWSER_FILE_LOG List of strings brows:debug,auth:debug A list of modules and their intended logging level for use in the file log.  
DAST_BROWSER_FILE_LOG_PATH string /output/browserker.log Set to the path of the file log.  
DAST_BROWSER_IGNORED_HOSTS List of strings site.com,another.com Hostnames included in this variable are accessed, not attacked, and not reported against.  
DAST_BROWSER_INCLUDE_ONLY_RULES List of strings 16.1,16.2,16.3 Comma-separated list of check identifiers to use for the scan.  
DAST_BROWSER_LOG List of strings brows:debug,auth:debug A list of modules and their intended logging level for use in the console log.  
DAST_BROWSER_LOG_CHROMIUM_OUTPUT boolean true Set to true to log Chromium STDOUT and STDERR.  
DAST_BROWSER_MAX_ACTIONS number 10000 The maximum number of actions that the crawler performs. For example, selecting a link, or filling a form.  
DAST_BROWSER_MAX_DEPTH number 10 The maximum number of chained actions that the crawler takes. For example, Click -> Form Fill -> Click is a depth of three.  
DAST_BROWSER_MAX_RESPONSE_SIZE_MB number 15 The maximum size of a HTTP response body. Responses with bodies larger than this are blocked by the browser. Defaults to 10 MB.  
DAST_BROWSER_NAVIGATION_STABILITY_TIMEOUT Duration string 7s The maximum amount of time to wait for a browser to consider a page loaded and ready for analysis after a navigation completes.  
DAST_BROWSER_NAVIGATION_TIMEOUT Duration string 15s The maximum amount of time to wait for a browser to navigate from one page to another.  
DAST_BROWSER_NUMBER_OF_BROWSERS number 3 The maximum number of concurrent browser instances to use. For shared runners on GitLab.com, we recommended a maximum of three. Private runners with more resources may benefit from a higher number, but are likely to produce little benefit after five to seven instances.  
DAST_BROWSER_PAGE_LOADING_SELECTOR selector css:#page-is-loading Selector that when is no longer visible on the page, indicates to the analyzer that the page has finished loading and the scan can continue. Cannot be used with DAST_BROWSER_PAGE_READY_SELECTOR  
DAST_BROWSER_PAGE_READY_SELECTOR selector css:#page-is-ready Selector that when detected as visible on the page, indicates to the analyzer that the page has finished loading and the scan can continue. Cannot be used with DAST_BROWSER_PAGE_LOADING_SELECTOR  
DAST_BROWSER_SCAN boolean true Required to be true to run a browser-based scan.  
DAST_BROWSER_SEARCH_ELEMENT_TIMEOUT Duration string 3s The maximum amount of time to allow the browser to search for new elements or user actions.  
DAST_BROWSER_STABILITY_TIMEOUT Duration string 7s The maximum amount of time to wait for a browser to consider a page loaded and ready for analysis.  
DAST_EXCLUDE_RULES string 10020,10026 Set to a comma-separated list of ZAP Vulnerability Rule IDs to exclude them from running during the scan. Rule IDs are numbers and can be found from the DAST log or on the ZAP project.  
DAST_EXCLUDE_URLS URLs https://example.com/.*/sign-out The URLs to skip during the authenticated scan; comma-separated. Regular expression syntax can be used to match multiple URLs. For example, .* matches an arbitrary character sequence.  
DAST_FULL_SCAN_ENABLED boolean true Set to true to run both passive and active checks. Default: false  
DAST_PATHS string /page1.html,/category1/page3.html Set to a comma-separated list of URL paths relative to DAST_WEBSITE for DAST to scan.  
DAST_PATHS_FILE string /builds/project/urls.txt Set to a file path containing a list of URL paths relative to DAST_WEBSITE for DAST to scan. The file must be plain text with one path per line.  
DAST_PKCS12_CERTIFICATE_BASE64 string ZGZkZ2p5NGd... The PKCS12 certificate used for sites that require Mutual TLS. Must be encoded as base64 text.  
DAST_PKCS12_PASSWORD string password The password of the certificate used in DAST_PKCS12_CERTIFICATE_BASE64. Create sensitive custom CI/CI variables using the GitLab UI.  
DAST_REQUEST_HEADERS string Cache-control:no-cache Set to a comma-separated list of request header names and values.  
DAST_SKIP_TARGET_CHECK boolean true Set to true to prevent DAST from checking that the target is available before scanning. Default: false.  
DAST_TARGET_AVAILABILITY_TIMEOUT number 60 Time limit in seconds to wait for target availability.  
DAST_WEBSITE URL https://example.com The URL of the website to scan.  
SECURE_ANALYZERS_PREFIX URL registry.organization.com Set the Docker registry base address from which to download the analyzer.  

Vulnerability detection

Vulnerability detection is gradually being migrated from the default Zed Attack Proxy (ZAP) solution to the browser-based analyzer. For details of the vulnerability detection already migrated, see browser-based vulnerability checks.

The crawler runs the target website in a browser with DAST/ZAP configured as the proxy server. This ensures that all requests and responses made by the browser are passively scanned by DAST/ZAP. When running a full scan, active vulnerability checks executed by DAST/ZAP do not use a browser. This difference in how vulnerabilities are checked can cause issues that require certain features of the target website to be disabled to ensure the scan works as intended.

For example, for a target website that contains forms with Anti-CSRF tokens, a passive scan works as intended because the browser displays pages and forms as if a user is viewing the page. However, active vulnerability checks that run in a full scan cannot submit forms containing Anti-CSRF tokens. In such cases, we recommend you disable Anti-CSRF tokens when running a full scan.

Managing scan time

It is expected that running the browser-based crawler results in better coverage for many web applications, when compared to the standard GitLab DAST solution. This can come at a cost of increased scan time.

You can manage the trade-off between coverage and scan time with the following measures:

  • Limit the number of actions executed by the browser with the variable DAST_BROWSER_MAX_ACTIONS. The default is 10,000.
  • Limit the page depth that the browser-based crawler checks coverage on with the variable DAST_BROWSER_MAX_DEPTH. The crawler uses a breadth-first search strategy, so pages with smaller depth are crawled first. The default is 10.
  • Vertically scale the runner and use a higher number of browsers with variable DAST_BROWSER_NUMBER_OF_BROWSERS. The default is 3.


Due to poor network conditions or heavy application load, the default timeouts may not be applicable to your application.

Browser-based scans offer the ability to adjust various timeouts to ensure it continues smoothly as it transitions from one page to the next. These values are configured using a Duration string, which allow you to configure durations with a prefix: m for minutes, s for seconds, and ms for milliseconds.

Navigations, or the act of loading a new page, usually require the most amount of time because they are loading multiple new resources such as JavaScript or CSS files. Depending on the size of these resources, or the speed at which they are returned, the default DAST_BROWSER_NAVIGATION_TIMEOUT may not be sufficient.

Stability timeouts, such as those configurable with DAST_BROWSER_NAVIGATION_STABILITY_TIMEOUT, DAST_BROWSER_STABILITY_TIMEOUT, and DAST_BROWSER_ACTION_STABILITY_TIMEOUT can also be configured. Stability timeouts determine when browser-based scans consider a page fully loaded. Browser-based scans consider a page loaded when:

  1. The DOMContentLoaded event has fired.
  2. There are no open or outstanding requests that are deemed important, such as JavaScript and CSS. Media files are usually deemed unimportant.
  3. Depending on whether the browser executed a navigation, was forcibly transitioned, or action:


After these events have occurred, browser-based scans consider the page loaded and ready, and attempt the next action.

If your application experiences latency or returns many navigation failures, consider adjusting the timeout values such as in this example:

  - template: DAST.gitlab-ci.yml

    DAST_WEBSITE: "https://my.site.com"
Adjusting these values may impact scan time because they adjust how long each browser waits for various activities to complete.


Using the latest version of the DAST template these artifacts are exposed for download by default.

The list of artifacts includes the following files:

  • gl-dast-debug-auth-report.html
  • gl-dast-debug-crawl-report.html
  • gl-dast-crawl-graph.svg


See troubleshooting for more information.