Hi Shunya,
The rule is use the characters a-z, A-Z, _ and -.
This change was made long time before. It looks like you are upgrading from an very old version.
Currently there is no feature in shortcoder to scan all the posts and identify the usage.
It would be beyond the scope of the plugin.
You have to delete this shortcode and create a new one with the new content.
You can search for the shortcode by old name in posts page using the search box. Then you have to manually search, replace and update the post with the new name. I understand it is a painful task, but this change is needed to bring in a standard and set some rules in the allowed characters.
Hope you understand.
Thanks,
Aakash
