Culprit:
(1) - validation/validate.jelly#L58
(2) - validation/validate.jelly#L71
(3) - validation/validate.jelly#L83-L99

Reproduction steps:

• Install LDAP or clone https://github.com/jenkinsci/ldap-plugin and then mvn hpi:run
• Go to Manage Jenkins > Configure Global Security
• In the "Security Realm" section, select "LDAP"
• Click on "Test LDAP settings" (1)
• Click on "Test" (2)

Screenshot attached about where the feature is displayed.

Proposal
https://www.jenkins.io/doc/developer/security/csp/#inline-event-handlers
https://www.jenkins.io/doc/developer/security/csp/#inline-javascript-blocks

Testing notes

• Ensure to reproduce the feature before any change
• Ensure that you reproduce the feature after you have made the change