[JENKINS-70719] Creating a new credential with an existing ID returns a 302 response code instead of blocking the submission

When attempting to add a new credential in Jenkins with an already existing ID, the user is notified that "This ID is already in use", however, the user is able to click on the 'create' button which results in a 302 status code. The expected behavior should be to block the submission in case of an already-used ID or return an error status.

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Originally reported by benipeled, imported from: Creating a new credential with an existing ID returns a 302 response code instead of blocking the submission

• status: Open
  
• priority: Minor
  
• component(s): credentials-plugin
  
• resolution: Unresolved
  
• votes: 0
  
• watchers: 1
  
• imported: 2025-12-08
  

Raw content of original issue

When attempting to add a new credential in Jenkins with an already existing ID, the user is notified that "This ID is already in use", however, the user is able to click on the 'create' button which results in a 302 status code. The expected behavior should be to block the submission in case of an already-used ID or return an error status.

• environment: Jenkins 2.389

1 attachment

- [image-2023-03-02-18-02-30-409.png](https://issues.jenkins.io/secure/attachment/60056/image-2023-03-02-18-02-30-409.png)
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Start by reproducing duplicate credential creation in the credentials-plugin using the Jenkins 2.389 scenario described in the issue. Trace the existing-ID validation and create submission, then verify that an already-used ID blocks submission or returns an error instead of a 302 response.

Written by the indexing model from the issue text.