Kingdom: Encapsulation

Encapsulation is about drawing strong boundaries. In a web browser that might mean ensuring that your mobile code cannot be abused by other mobile code. On the server it might mean differentiation between validated data and unvalidated data, between one user's data and another's, or between data users are allowed to see and data that they are not.

HTML5: Deprecated Header

Abstract
Use of a deprecated header can enable attackers to cause unexpected behaviour in web browsers
Explanation
HTTP headers are key-value pairs sent between the client and server to provide additional information for handling HTTP requests and responses. Browser vendors mark some HTTP headers as deprecated when they no longer maintain, support, or enhance implementation of the header. Usage of these headers might create a false sense of security and increase the site's vulnerability.

Developers should rely on HTTP headers specified in the HTML standard[3] as they are supported uniformly across browsers. Using non-standard headers might provide additional features and controls but comes with limited browser support and risk of deprecation.

For example, the X-XSS-Protection header was used by developers to control the browser's behavior and offer protection against cross-site scripting (XSS). Modern browsers have better built-in protections with the use of Content Security Policy. Therefore, relying on X-XSS-Protection header can introduce new risks.
References
[1] X-XSS-Protection - HTTP | MDN
[2] IE8 XSS Filters
[3] HTML Standard
[4] Standards Mapping - Common Weakness Enumeration CWE ID 477
[5] Standards Mapping - DISA Control Correlation Identifier Version 2 CCI-001368, CCI-001414
[6] Standards Mapping - General Data Protection Regulation (GDPR) Indirect Access to Sensitive Data
[7] Standards Mapping - NIST Special Publication 800-53 Revision 4 AC-4 Information Flow Enforcement (P1)
[8] Standards Mapping - NIST Special Publication 800-53 Revision 5 AC-4 Information Flow Enforcement
[9] Standards Mapping - OWASP Application Security Verification Standard 4.0 1.14.6 Configuration Architectural Requirements (L2 L3)
[10] Standards Mapping - OWASP Mobile 2014 M1 Weak Server Side Controls
[11] Standards Mapping - OWASP Mobile 2024 M8 Security Misconfiguration
[12] Standards Mapping - OWASP Top 10 2010 A6 Security Misconfiguration
[13] Standards Mapping - OWASP Top 10 2013 A5 Security Misconfiguration
[14] Standards Mapping - OWASP Top 10 2017 A6 Security Misconfiguration
[15] Standards Mapping - OWASP Top 10 2021 A05 Security Misconfiguration
[16] Standards Mapping - Payment Card Industry Data Security Standard Version 1.1 Requirement 6.5.10
[17] Standards Mapping - Payment Card Industry Data Security Standard Version 3.1 Requirement 6.5.6
[18] Standards Mapping - Payment Card Industry Data Security Standard Version 3.2 Requirement 6.5.6
[19] Standards Mapping - Payment Card Industry Data Security Standard Version 3.2.1 Requirement 6.5.6
[20] Standards Mapping - Payment Card Industry Data Security Standard Version 4.0 Requirement 6.2.4
[21] Standards Mapping - Payment Card Industry Data Security Standard Version 4.0.1 Requirement 6.2.4
[22] Standards Mapping - Payment Card Industry Software Security Framework 1.0 Control Objective 4.2 - Critical Asset Protection
[23] Standards Mapping - Payment Card Industry Software Security Framework 1.1 Control Objective 4.2 - Critical Asset Protection
[24] Standards Mapping - Payment Card Industry Software Security Framework 1.2 Control Objective 4.2 - Critical Asset Protection
[25] Standards Mapping - Security Technical Implementation Guide Version 4.2 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[26] Standards Mapping - Security Technical Implementation Guide Version 4.3 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[27] Standards Mapping - Security Technical Implementation Guide Version 4.4 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[28] Standards Mapping - Security Technical Implementation Guide Version 4.5 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[29] Standards Mapping - Security Technical Implementation Guide Version 4.6 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[30] Standards Mapping - Security Technical Implementation Guide Version 4.7 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[31] Standards Mapping - Security Technical Implementation Guide Version 4.8 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[32] Standards Mapping - Security Technical Implementation Guide Version 4.9 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[33] Standards Mapping - Security Technical Implementation Guide Version 4.10 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[34] Standards Mapping - Security Technical Implementation Guide Version 4.11 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[35] Standards Mapping - Security Technical Implementation Guide Version 4.1 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[36] Standards Mapping - Security Technical Implementation Guide Version 5.1 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[37] Standards Mapping - Security Technical Implementation Guide Version 5.2 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[38] Standards Mapping - Security Technical Implementation Guide Version 5.3 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[39] Standards Mapping - Security Technical Implementation Guide Version 6.1 APSC-DV-000480 CAT II, APSC-DV-000490 CAT II
[40] Standards Mapping - Web Application Security Consortium Version 2.00 Application Misconfiguration (WASC-15)
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