ServiceNow platform allows attaching files on the form even though the file name is too large. But once the file is attached, the name gets truncated from the end along with the extension.
This issue can occur in any release/version.
The attached file will not be effected. It can be used (view/download) further as the file name doesn't show up in the UI only, back end it remains the same (along with extension).
The file name will be visible till 100 characters and rest will be truncated.
This is an example where a word file with 235 characters in the name was attached to an incident.