Class HiddenHTMLDetector

Detects instructions hidden via CSS/HTML that are invisible to humans but parsed by LLMs. This is the most common content injection vector.

Covers:

• CSS display:none / visibility:hidden elements with text content
• Off-screen positioned elements (position:absolute with extreme offsets)
• Zero-size elements (width:0, height:0, font-size:0)
• Background-matching text color
• Opacity:0 elements