Bugfix/workflow vulnerability comparison (#569)

.github/workflows/vulnerability-comparison.yaml

@@ -11,6 +11,7 @@ env:
 
 jobs:
   vulnerability-comparison:
+    if: github.event.pull_request.head.repo.full_name == github.repository
     runs-on: ubuntu-latest
     permissions:
       pull-requests: write
@@ -21,7 +22,7 @@ jobs:
           ref: ${{ env.SHA }}
       - name: Set short SHA
         id: vars
-        run: echo "SHA_SHORT=$(echo $GITHUB_SHA | cut -c1-7)" >> $GITHUB_ENV
+        run: echo "SHA_SHORT=$(git rev-parse --short HEAD)" >> $GITHUB_ENV
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@v3
       - name: Build and push Docker image