Tracking, Propagation Attacks, and What We Found in Real Email Traffic

This detailed write-up covers several advanced techniques used by email senders to track recipients beyond traditional pixel tracking methods. Here’s a summary of key points:

Key Techniques Covered

1. CSS Media Query Conditional Loading:

   • Email senders can embed tracking URLs in CSS media queries, which load based on user preferences (e.g., dark mode).
   • Example:

     css
      
     1@media (prefers-color-scheme: dark) {
     2  body { background-image: url('https://tracker.esp.com/dark/PERRECIPIENTTOKEN'); }
     3}

2. Meta Tag Embedding:

   • Tracking tokens can be embedded in meta tags, which survive quoted replies.
   • Example:

     html
      
     1<meta name="campaign" content="CAMPAIGN123/PERRECIPIENTTOKEN">

3. Direct URL Tracking (No Redirects):

   • Links directly embed tracking tokens without using redirect URLs.
   • Example:

     plaintext
      
     1https://nextdoor.com/news_feed/?ct=ABCDEF123&ec=GHIJ456&token=UNIQUE789
     2``

Read the full article at DEV Community

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