What are the security risks of using Gitlab CI shared test runners?
<p>I am trying to host a new project with Gitlab. It is a private Python project. I was able to test some initial tests with Gitlab CI.</p>

<p>I don't use cache while running tests,</p>

<p>While exploring the runner section in settings, there is a warning shown,</p>

<blockquote>
  <p>GitLab Runners do not offer secure isolation between projects that
  they do builds for. You are TRUSTING all GitLab users who can push
  code to project A, B or C to run shell scripts on the machine hosting
  runner X.</p>
</blockquote>

<p>what are the security risks in using a shared test runner? Is it safe to run private projects on a shared runner? What precautions can be taken while running tests on a shared runner?</p>

<p>Thank you for any insight.</p>