Add how to include secure templates in MR pipeline

doc/ci/merge_request_pipelines/index.md

@@ -128,6 +128,12 @@ This helps you avoid having to add the `only:` rule to all of your jobs to make
 them always run. You can use this format to set up a Review App, helping to
 save resources.
 
+### Using SAST, DAST, and other Secure Templates with Pipelines for Merge Requests 
+
+To use [Secure templates](https://gitlab.com/gitlab-org/gitlab/-/tree/master/lib/gitlab/ci/templates/Security)
+with pipelines for merge requests, you may need to apply a `rules: if: merge_request_event` for the
+Secure scans to run in the same pipeline as the commit.
+
 #### Excluding certain branches
 
 Pipelines for merge requests require special treatment when