Threat Intelligence

How Simple Web Styling Code Could Be Used to Steal Your Email Data

Dark Reading · 6 Aug 2026

Key Takeaway Don't assume only obvious threats like links or attachments are risky — talk to your email provider or IT support about how they defend against newer, less visible techniques like CSS-based data exfiltration.

CSS (Cascading Style Sheets) has long been considered a harmless tool used to control the look and layout of websites and emails — fonts, colours, spacing, and design. However, researchers have found that this seemingly benign code can be manipulated to quietly extract sensitive information from webmail platforms without a user ever noticing.

Because CSS is not typically treated as a security risk, many email providers focus their defences on more obvious threats like malicious links, attachments, or scripts. This gap means attackers could potentially hide data-stealing techniques inside styling code that slips past existing filters, putting user inboxes at risk of silent data leaks.

For small businesses, this is a reminder that cyber threats can come from unexpected and overlooked corners of everyday technology, not just the obvious scams or suspicious downloads. As email remains a core communication tool for most businesses, staying informed about emerging techniques like this helps ensure your protections keep pace with how attackers are evolving.

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Summarised by CISO AI from Dark Reading. We link back to every original so you can read it yourself.