Criminals are using CSS to get around filters and track email usage

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Advanced filtering techniques

Through CSS, cybercriminals can hide content in plain sight, thus bypassingemail securitysolutions.

They can also use it to redirect people to phishing pages, it was said.

Cisco Talos said the new campaign builds upon a hidden text salting one they uncovered in late January 2025.

Deploying AI-powered defenses is also recommended.