Dropbox OAuth2 Issue: Scope Parameter Handling

Question

According to OAuth2 Authorization documentation, the scope parameter is nullable, and as per RFC 6749, parameters without a value must be treated as omitted, with unrecognized parameters ignored.

However, Dropbox's OAuth2 implementation returns the following error when the scope parameter is included:

Error:

"error": "invalid_request",

"error_description": "unknown field \"scope\""

This behavior violates OAuth2 standards, as unrecognized parameters should not cause a failure.

DB-Des · Answer

Vivek_Yadav,
I have submitted a request for the team to further investigate the reported issue. We'll follow up here once there is an update.

DB-Des · Answer

Hi Vivek_Yadav,
Including the scope parameter without value in the Auth URL does omit it and allows authorization to continue.
For example, the following two Auth URLs work without issues:

https://www.dropbox.com/oauth2/authorize?client_id=&lt;APP_KEY&gt;&amp;response_type=code&amp;scope
https://www.dropbox.com/oauth2/authorize?client_id=&gt;APP_KEY&gt;&amp;response_type=code&amp;scope=

&nbsp;
In order to further investigate the error you have reported, please reply with:

the steps to reproduce the issue, including relevant code snippet(s), but don't include any access or refresh token(s)
the full text of any error or unexpected output

Vivek_Yadav · Answer

Hi DB-DesThis happens when we send the token request with grant type as authorization code and empty scope parameter i.e. without a value.Based on the RFC, Dropbox should be ignoring parameters they don't recognize as valid, not failing the request.Last para of RFC 6749 - The OAuth 2.0 Authorization Framework

Vivek_Yadav · Answer

DB-Des · Answer

Hi Vivek_Yadav&nbsp;
The oauth2/token endpoint allows the scope parameter only with a refresh_token because it aligns with OAuth 2.0 standards and best practices.
When using a refresh token, the scope parameter lets you request a subset of the originally granted permissions, ensuring least-privilege access and better security. For other grant types (such as authorization_code in your example), the scope is determined during the initial authorization process, based on user consent. Allowing the scope parameter in these cases could bypass this consent, potentially introducing security risks.
Further, RFC 6749 § 4.1.3, does not require the scope parameter, nor does it list it as optional, when using authorization_code as the grant type.
This restriction ensures compliance with the OAuth specification and helps maintain secure, user-approved access to resources.
Let us know if you have further concerns.

Forum Discussion

Dropbox OAuth2 Issue: Scope Parameter Handling

About Dropbox API Support & Feedback

Related Content

What's the correct way to handle expired access token

Can Dropbox handle git repostories? ONLY as a secondary backup?

I have a handle leak from Dropbox?

Query Dropbox API with `select_user` URL parameter

iOS 11 - Dropbox app not handling NSURLs from UIActivityItemProvider objects

Recent Discussions

Unable to Retrieve Dropbox "path_display" for Folders in Google Sheets Script

OIDC Using .NET SDK

How can I create Dropbox autosync feature for my app ?

How to filter events in dotnet SDK ?

When logging in to Android SDK, the account is not registered and registration fails