Isnt't there a : too much? I.e. shouldn't the snippet look like this:

include:
  - template: Security/SAST.gitlab-ci.yml

security-code-scan-sast: # no '::' here
  variables:
    SAST_ANALYZER_IMAGE_TAG: 3 

Thanks @nxt.cma for pointing this mistake out, I've updated the snippet!

@nxt.cma My project has been set up as you said before, but I still get an error。Could you help me solve the problem?

/root/.dotnet/msbuild/Sdks/Microsoft.NET.Sdk/Sdk/Sdk.props(40,3): error MSB4019: The imported project "/usr/lib/mono/xbuild/Current/Microsoft.Common.props" was not found. Confirm that the expression in the Import declaration "/usr/lib/mono/xbuild/Current/Microsoft.Common.props" is correct, and that the file exists on disk.