You can fix it yourself by editing this file:
wp-content/plugins/addthis/backend/AddThisPlugin.php around line 846.
Find: $script .= ' <script data-cfasync="false" type="text/javascript"'
Replace: $script .= ' <script data-cfasync="false" type="text/javascript" '
Also, according to W3C HTML5 validation, type is not even needed anymore, so it can be:
Replace: $script .= ' <script data-cfasync="false" '
Note that unless the developer fixes it, the next update will undo the fix outlined above.
