Filter.ExtractStyleBlocks.Scope
TYPE: string/null
VERSION: 3.0.0
DEFAULT: NULL
ALIASES: Filter.ExtractStyleBlocksScope, FilterParam.ExtractStyleBlocksScope
--DESCRIPTION--

<p>
  If you would like users to be able to define external stylesheets, but
  only allow them to specify CSS declarations for a specific node and
  prevent them from fiddling with other elements, use this directive.
  It accepts any valid CSS selector, and will prepend this to any
  CSS declaration extracted from the document. For example, if this
  directive is set to <code>#user-content</code> and a user uses the
  selector <code>a:hover</code>, the final selector will be
  <code>#user-content a:hover</code>.
</p>
<p>
  The comma shorthand may be used; consider the above example, with
  <code>#user-content, #user-content2</code>, the final selector will
  be <code>#user-content a:hover, #user-content2 a:hover</code>.
</p>
<p>
  <strong>Warning:</strong> It is possible for users to bypass this measure
  using a naughty + selector. This is a bug in CSS Tidy 1.3, not HTML
  Purifier, and I am working to get it fixed. Until then, HTML Purifier
  performs a basic check to prevent this.
</p>
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