If you only want to hide the banner for yourself or a specific set of users, you can use browser-based tools: Google Apps Script remove warning banner - Stack Overflow

Because the web app is hosted on the ://google.com domain, Google injects this iframe header as a security measure to prevent phishing and spoofing. Even with a Google Workspace (formerly G Suite) Business or Enterprise account, the banner remains.

Use a verified domain and support links

: If you're still unsure, consider reaching out to Google Support or posting your question on a relevant forum (like the Google Apps Script community on Stack Overflow).

The message “This application was created by a Google Apps Script user” is a security feature, not a bug. It protects users from malicious scripts. However, for legitimate developers, it creates unnecessary friction.

When you deploy and set access to "Anyone within [Your Domain]," the banner is removed for your colleagues. Verification: