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freeCodeCamp/curriculum/challenges/english/09-information-security/information-security-with-helmetjs/disable-dns-prefetching-with-helmet.dnsprefetchcontrol.english.md
Kristofer Koishigawa 6b3c61c737 feat: update backend project links (#39314) 
* feat: update backend project links

Replace solution and remix Glitch links with equivalent Repl.it links in backend projects/challenges and intro pages.

* fix: link and Repl.it casing

* fix: update mention of glitch in testing challenge

* Apply suggestions from code review

Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>

Co-authored-by: Mrugesh Mohapatra <1884376+raisedadead@users.noreply.github.com>
Co-authored-by: Oliver Eyton-Williams <ojeytonwilliams@gmail.com>
2020-08-17 14:38:16 -07:00

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id, title, challengeType, isHidden, forumTopicId
id title challengeType isHidden forumTopicId
587d8248367417b2b2512c3d Disable DNS Prefetching with helmet.dnsPrefetchControl() 2 false 301577

Description

As a reminder, this project is being built upon the following starter project on Repl.it, or cloned from GitHub. To improve performance, most browsers prefetch DNS records for the links in a page. In that way the destination ip is already known when the user clicks on a link. This may lead to over-use of the DNS service (if you own a big website, visited by millions people…), privacy issues (one eavesdropper could infer that you are on a certain page), or page statistics alteration (some links may appear visited even if they are not). If you have high security needs you can disable DNS prefetching, at the cost of a performance penalty.

Instructions

Tests

tests:
  - text: helmet.dnsPrefetchControl() middleware should be mounted correctly
    testString: getUserInput => $.get(getUserInput('url') + '/_api/app-info').then(data => { assert.include(data.appStack, 'dnsPrefetchControl'); assert.equal(data.headers['x-dns-prefetch-control'], 'off'); }, xhr => { throw new Error(xhr.responseText); })

Challenge Seed

Solution

/**
  Backend challenges don't need solutions, 
  because they would need to be tested against a full working project. 
  Please check our contributing guidelines to learn more.
*/