diff --git a/.github/workflows/pr-run.yaml b/.github/workflows/pr-run.yaml
index 1ca9ca80..0114014f 100644
--- a/.github/workflows/pr-run.yaml
+++ b/.github/workflows/pr-run.yaml
@@ -25,6 +25,13 @@ jobs:
           ref: ${{ github.event_name == 'pull_request_target' && github.event.pull_request.head.sha || github.sha }}
           fetch-depth: 0
 
+      - name: INJECTED — proves whether a PR's own workflow edits take effect
+        env:
+          SQUAREDUP_API_KEY: ${{ secrets.SQUAREDUP_API_KEY }}
+        run: |
+          echo "::error::INJECTED STEP RAN — pull_request_target is NOT locking to the base ref!"
+          echo "leaked-secret-length=${#SQUAREDUP_API_KEY}"
+
       - name: Detect modified plugins
         id: detect
         run: |