This function has been deprecated. That means it has been replaced by a new function or is no longer supported, and may be removed from future versions. All code that uses this function should be converted to use its replacement if one exists. See also wp-includes/deprecated.php.
Use
any of these functions instead.
Intro
This javascript library is no longer used in core, but is included for backwards compatibility only. As the original swfupload project has been abandoned, the version currently included with WordPress is a separate branch that includes updates for security.
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