[Bug] Removing idSite URL parameter when in MultiSites view causes odd error

[jalavosus]

What happened?

After removing idSite parameter from URL when in MultiSites module, user is kicked to a sign-in page with an error.

What should happen?

MultiSites view should work without idSite URL parameter.

How can this be reproduced?

0. Have a Matomo Cloud instance with multiple sites configured.

Go to MultiSites view by:

1. Logging in to a Matomo instance with multiple sites configured.
2. Clicking "All Websites" in the top right corner

Cause crash/error:

1. In URL, remove idSite parameter. Ex: index.php?module=MultiSites&action=index&idSite=2 --> index.php?module=MultiSites&action=index.
2. Hit "Enter", "Go", etc.
3. Get booted to weird signin screen with error:

Note: a sign-in isn't actually necessary here, simply clicking "back" brings everything back to normal (as the URL is reverted).

Matomo version

Latest Matomo Cloud

PHP version

No response

Server operating system

No response

What browsers are you seeing the problem on?

Chrome, Microsoft Edge, Not applicable (e.g. an API call etc.)

Computer operating system

macOS Sequoia 15.0.1

Relevant log output

No response

Validations

• Read our Contributing Guidelines.
• Follow our Security Policy.
• Check that there isn't already an issue that reports the same bug to avoid creating duplicates.
• The provided steps to reproduce is a minimal reproducible of the Bug.

[michalkleiner]

Hi @jalavosus, can you share what is the use case for removing the url parameter? Yes, we acknowledge Matomo may get into an unexpected state if you remove some URL parts, sometimes unexpectedly so, but it would be good to know what the use case might be if any at all.

[sgiehl]

somehow similar to #22788. There is a general problem when idsite param may be missing or might contain an invalid site id.