title: Cannot install plugin on JIRA Server
body: <p>We have JIRA-Software 7 running on a custom docker machine with a Postgres DB and nginx as a reverse proxy (SSL). The custom domain is <a href="https://jira.url.de" rel="nofollow noreferrer">https://jira.url.de</a> and is working so far. Installation has not been a problem.</p>
  <p>But now i wanted to install a plugin and i get the following error:
  <code>An unexpected error has occurred. Please refer to the logs for more information.</code></p>
  <p>First of all where can i find the logs?</p>
  <p>Second - i found out that if i click on &quot;Manage Add-on i will be directed to  a 500 error on <code>http://127.0.0.1:8080/plugins/servlet/upm</code></p>
  <p>I read somewhere about configuring the server.xml file in order to correct the plugin url. But how can i edit this file? I can not find it inside the docker container.</p>
  <h1>UPDATE</h1>
  <p>if i try to update the <em>Atlassian Universal Plugin Manager Plugin</em> i get the following console Notice:</p>
  <p><code>[blocked] The page at https://jira.url.de/plugins/servlet/upm was not allowed to display insecure content from http://127.0.0.1:8080/rest/plugins/self-update/1.0/.</code></p>