#10245 modernized the Jenkins header. It adds the class "jenkins-avatar" to all icons in the header, thereby having them all overlayed with a circular mask. Custom icons can have a square shape and are wrongly cut by that circular mask.



For reproduction install a plugin with custom global actions (most simple: sidebar plugin, which can add arbitrary custom global actions).

Be aware that screenshot is with custom header plugin installed, but custom header plugin does not cause this (clarified in jenkinsci/customizable-header-plugin#215

The relevant line is probably 

  

    

      jenkins/core/src/main/resources/lib/layout/header/actions.jelly
    
    

         Line 49
      in
      60df855
    
  
  

    


        

          

          
 <l:icon src="${icon}" class="jenkins-avatar" /> 
        
    
  



I could create a PR to simply remove the class attribute but I'm not sure if I can easily test this locally, given I'm behind a company proxy that interferes with the maven build.