Silverlight

1. Historical Role of Silverlight in Browser Fingerprinting

Silverlight (Microsoft’s browser plugin, analogous to Adobe Flash) was intermittently used in fingerprinting from 2007–2020, primarily through:

1. navigator.plugins Enumeration Browsers exposed installed plugins (e.g., Silverlight Plug-In 5.1.50918.0), allowing scripts to detect presence/version—a high-entropy fingerprint vector.

2. ActiveX Probing (IE-Only) Legacy Internet Explorer allowed instantiation via new ActiveXObject('AgControl.AgControl'), revealing system-specific control interfaces.

3. MIME Type Checks Even inactive plugins could be detected via navigator.mimeTypes['application/x-silverlight-2'].

4. Rendering Artifacts Silverlight’s graphics pipeline (e.g., font smoothing) introduced measurable deviations in Canvas/WebGL output.

2. Why Silverlight is Obsolete in Modern Fingerprinting

Technical Deprecation:

• NPAPI Removal: Chrome (2015), Firefox (2017), and Edge dropped NPAPI support. Plugins like Silverlight/Java now fail to load.
• API Neutralization:
  • navigator.plugins returns an empty/fixed array.
  • navigator.mimeTypes is frozen.
  • ActiveX is restricted to IE Enterprise Mode (disabled by default).

Security & Relevance:

• Unpatched Vulnerabilities: Silverlight’s last update (v5.1, 2019) left critical flaws like CVE-2016-0034 unaddressed.
• Negligible Fingerprint Value: With 99.8% of users lacking Silverlight (per StatCounter), detection yields no meaningful entropy.

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