FAQ-001121 - Lightning Web Components and JavaScript Security / Component Design and Security Compliance

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Current FAQ

Question
How do I design LWC components that comply with security requirements while maintaining necessary UI functionality?
Answer
To design LWC components that comply with security requirements while maintaining necessary UI functionality, follow these best practices: 1. **Use Static Resources**: Include all scripts and styles as static resources in your package. Avoid dynamically loading JavaScript or CSS directly into components. 2. **Enable LockerService**: Use API version 40 or later to ensure LockerService is enabled, providing namespace isolation and preventing cross-namespace security issues. 3. **Sanitize User Data**: Sanitize any user-controlled data before rendering it in the component. Use secure filters or libraries to prevent vulnerabilities like cross-site scripting (XSS). Avoid binding user-controlled data to unsafe attributes like `iframe src` or `a href` without proper sanitization. 4. **CSS Positioning**: Avoid using `position: absolute` or `position: fixed` in component CSS unless the component is not exposed outside the namespace or is limited to specific pages. This prevents interference with other UI elements. 5. **Secure Attributes**: Be cautious with attributes in the expression language. Sanitize values in the controller or use private variables to bind sanitized data. 6. **Community Declaration**: Explicitly declare components as available for communities if they are intended for use outside Salesforce internal pages. 7. **Avoid Inline JavaScript**: Do not use inline JavaScript in web links or other components, as it can bypass namespace isolation and create security risks. 8. **Prevent Clickjacking**: Avoid styles like `position: absolute` that could lead to clickjacking vulnerabilities. Ensure components do not obscure other UI elements. By adhering to these guidelines, you can ensure your LWC components are secure and functional.

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Related Security Rules (click to view)
AvoidAuraWithLockerDisabledAvoidUnescapedHtmlInAura@lwc/lwc/no-inner-htmlApexXSSFromEscapeFalseApexXSSFromURLParamAvoidJavaScriptInUrlsLoadJavaScriptIncludeScriptLoadJavaScriptHtmlScriptLoadCSSLinkHrefLoadCSSApexStylesheetAvoidCreateElementScriptLinkTag
Question
How do I design LWC components that comply with security requirements while maintaining necessary UI functionality?
Recommended Answer Update
To design LWC components that comply with security requirements while maintaining necessary UI functionality, follow these best practices: 1. **Use Static Resources**: Include all scripts and styles as static resources in your package. Avoid dynamically loading JavaScript or CSS directly into components. 2. **Enable LockerService**: Use API version 40 or later to ensure LockerService is enabled, providing namespace isolation and preventing cross-namespace security issues. 3. **Sanitize User Data**: Sanitize any user-controlled data before rendering it in the component. Use secure filters or libraries to prevent vulnerabilities like cross-site scripting (XSS). Avoid binding user-controlled data to unsafe attributes like `iframe src` or `a href` without proper sanitization. 4. **CSS Positioning**: Avoid using `position: absolute` or `position: fixed` in component CSS unless the component isn't exposed outside the namespace or is limited to specific pages. This prevents interference with other UI elements. 5. **Secure Attributes**: Be cautious with attributes in the expression language. Sanitize values in the controller or use private variables to bind sanitized data. 6. **Community Declaration**: Explicitly declare components as available for communities if they're intended for use outside Salesforce internal pages. 7. **Avoid Inline JavaScript**: Don't use inline JavaScript in web links or other components, as it can bypass namespace isolation and create security risks. 8. **Prevent Clickjacking**: Avoid styles like `position: absolute` that could lead to clickjacking vulnerabilities. Ensure components don't obscure other UI elements. By adhering to these guidelines, you can ensure your LWC components are secure and functional.
Reasoning
The answer is comprehensive and accurate, requiring only minor refinements to improve clarity and tone. Changed 'Do not use' to 'Don't use' for more conversational tone, and 'components are not exposed' to 'components aren't exposed' for better readability. These changes align with the brand guidelines for being conversational while maintaining all technical accuracy. The related security rules were selected because they directly apply to the security practices discussed: AvoidAuraWithLockerDisabled relates to point 2 about LockerService, AvoidUnescapedHtmlInAura and @lwc/lwc/no-inner-html relate to point 3 about sanitizing user data, ApexXSSFromEscapeFalse and ApexXSSFromURLParam relate to XSS prevention mentioned in point 3, AvoidJavaScriptInUrls relates to point 7 about avoiding inline JavaScript, LoadJavaScriptIncludeScript and LoadJavaScriptHtmlScript relate to point 1 about using static resources, LoadCSSLinkHref and LoadCSSApexStylesheet relate to CSS handling mentioned in point 1, and AvoidCreateElementScriptLinkTag relates to dynamic loading prevention in point 1.
Reasoning References