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Threat Model Analysis for flexmonkey/blurable

Threat: Client-Side Denial of Service (DoS) via Image Bomb

  • Description: An attacker could force the application to process an extremely large image or a very high number of images using blurable.js, consuming excessive client-side resources. This can be achieved by injecting malicious code or manipulating input to process images far beyond intended limits.

    • Impact: User's browser becomes unresponsive or crashes, effectively denying them access to the application and potentially other browser functionalities. This leads to a significant negative user experience and loss of application availability for the victim.

    • Blurable Component Affected: Core blurring functionality, specifically the image processing module within blurable.js.

    • Risk Severity: High

    • Mitigation Strategies:

      • Client-Side Input Validation: Implement strict limits on the size and dimensions of images processed by blurable.js. Validate image sources (URLs, file uploads) to prevent processing of excessively large or malicious images.
      • Server-Side Image Pre-processing: Resize and optimize images on the server before sending them to the client for blurring. This reduces the client-side processing burden.
      • Rate Limiting: Implement rate limiting on blurring operations, especially if triggered by user actions or external events, to prevent abuse.
      • Lazy Loading: Load and blur images only when they are visible in the viewport to minimize initial resource consumption and avoid processing unnecessary images.

Threat: Information Leakage via Reversible Blurring (Privacy/Security Bypass)

  • Description: If blurable.js is used client-side to blur sensitive information in images for privacy or security purposes, the blurring might be insufficient to protect the data. An attacker could employ image processing techniques or even simple visual inspection to reverse or bypass the blurring and reveal the original sensitive information. This is especially concerning if weak blur parameters are used or if the underlying data is highly discernible even when blurred.

    • Impact: Disclosure of sensitive information intended to be protected by blurring (e.g., personal data, confidential text, obscured faces). This constitutes a privacy violation and a security breach if blurring is relied upon as a security control.

    • Blurable Component Affected: The blurring algorithm itself and its effectiveness in obscuring information, as implemented by blurable.js. The application's design that relies on client-side blurring for security is also a contributing factor.

    • Risk Severity: Critical

    • Mitigation Strategies:

      • Eliminate Client-Side Blurring for Security: Do not rely on client-side blurring as a primary or sole security mechanism for protecting sensitive data. Client-side code is inherently untrusted and can be manipulated.
      • Server-Side Redaction/Anonymization: Perform redaction, anonymization, or other robust data masking techniques on the server before images are sent to the client. This ensures sensitive data is never exposed to the client-side.
      • Stronger Obfuscation Techniques (If Client-Side Blurring is Absolutely Necessary for UI/UX): If client-side blurring is used for non-security related privacy enhancement (e.g., UI/UX purposes only), use a sufficiently high blur radius and consider combining it with other obfuscation methods like pixelation or masking to increase the difficulty of reversing the effect. However, understand this is still not a security measure.
      • Security Testing of Blurring (If Client-Side Blurring is Used): If client-side blurring is used even for UI/UX privacy, rigorously test its effectiveness by attempting to reverse-engineer blurred images to ensure they adequately obscure the intended information and do not inadvertently leak sensitive details.
      • User Education: If client-side blurring is used for any privacy-related features, clearly educate users about its limitations and that it should not be considered a robust security measure for highly sensitive information.