Manual:$wgDisableUploadScriptChecks

Files and file uploads: $wgDisableUploadScriptChecks
Whether to disable the upload system's checks for HTML/JavaScript.
Introduced in version:1.19.0
Removed in version:still in use
Allowed values:(boolean)
Default value:false

Details edit

Whether to disable the upload system's checks for HTML/JavaScript.

  Warning: Setting this to true is very dangerous on a publicly editable site, so use $wgGroupPermissions to restrict uploading to only those that you trust.