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JavaScript & Security

• Describe a few ways that JavaScript can be used maliciously.
• What is a cookie and how can developers use/code them?
• What are the security implications of cookies?
• Describe terms, methods and other components you learned in this week’s lesson.
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• • Describe a few ways that JavaScript can be used maliciously,

  • What is a cookie and how can developers use/code them?,

  • What are the security implications of cookies?,

  • Describe terms methods and other components you learned in this week’s lesson,

  • (no fifth question provided—added placeholder to complete requested five)

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  Comprehensive General Answer

  1. Malicious Uses of JavaScript

  JavaScript is a powerful client‑side scripting language, but it can also be misused when handled improperly. A few common malicious uses include:

  • Cross‑Site Scripting (XSS): Attackers inject JavaScript into websites so it runs in the browsers of unsuspecting users. This can steal cookies, session tokens, or personal data.

  • Keylogging: Malicious JavaScript can record keystrokes entered into forms and send them to attackers.

  • Redirects to Malicious Sites: Embedded scripts can automatically redirect users to phishing or malware websites.

  • Form Manipulation: JavaScript can alter what fields submit, allowing attackers to hijack login requests or change payment information.

  • Browser Exploit Delivery: JavaScript can be used to detect browser vulnerabilities and deliver harmful payloads.

  These risks highlight the importance of sanitizing user input and enforcing strong security measures.

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  2. What Is a Cookie & How Developers Use Them

  A cookie is a small text file stored on a user’s browser. It holds data that allows a website to remember information between visits.

  Developers use cookies for:

  • Session management (keeping users logged in)

  • User preferences (themes, language settings)

  • Tracking user behavior for analytics

  • Storing input or temporary data to enhance the browsing experience

  Basic JavaScript cookie code:

  document.cookie = "username=Alex; expires=Tue, 10 Feb 2026 12:00:00 UTC; path=/";


  Reading a cookie:

  let cookies = document.cookie;


  Cookies allow websites to create a more personalized and functional user experience.

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  3. Security Implications of Cookies

  Cookies introduce several security concerns:

  • Cookie Theft via XSS: If attackers steal session cookies, they can impersonate users.

  • Session Hijacking: Stolen cookies can grant access to secure accounts.

  • Cross‑Site Request Forgery (CSRF): Attackers exploit the fact that browsers automatically send cookies to a site.

  • Unencrypted Cookies: If not transmitted over HTTPS, they can be intercepted during network transmission.

  • Persistent Tracking: Cookies can track user behavior across websites, raising privacy concerns.

  To prevent these issues, developers can use attributes like:

  • Secure: Ensures cookies are sent only over HTTPS

  • HttpOnly: Prevents JavaScript from reading the cookie

  • SameSite: Protects against CSRF

  • Short Expiration Times: Reduces risk window

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  4. Terms, Methods, and Components Learned This Week

  This week’s lesson introduced several important concepts related to client‑side scripting and cookies:

  • document.cookie: JavaScript property for setting and reading cookies

  • Cookie attributes:

    • expires – sets expiration date

    • path – defines which parts of the site can access the cookie

    • Secure, HttpOnly, SameSite – security flags

  • Prompt windows:

    • prompt() for receiving input from users

  • DOM Manipulation:

    • Changing elements using document.getElementById()

  • Events:

    • onclick, onload, etc., to trigger JavaScript actions

  • Client‑side validation:

    • Ensures data is correct before reaching the server

  • Basic JavaScript syntax: