diff --git a/github-actions/previews/upload-artifacts-to-firebase/action.yml b/github-actions/previews/upload-artifacts-to-firebase/action.yml
index 229f90dfd..84447c5ad 100644
--- a/github-actions/previews/upload-artifacts-to-firebase/action.yml
+++ b/github-actions/previews/upload-artifacts-to-firebase/action.yml
@@ -66,13 +66,34 @@ runs:
     - name: Extracting workflow artifact into Firebase public directory.
       shell: bash
       run: |
+        set -euo pipefail
+
         extractDir="$RUNNER_TEMP/artifact-unpack"
+        publicDir='${{inputs.firebase-public-dir}}'
 
-        mkdir -p '${{inputs.firebase-public-dir}}'
+        mkdir -p "$publicDir"
         mkdir -p "$extractDir"
 
         unzip unsafe-artifact.zip -d "$extractDir"
-        tar -xvzf "$extractDir/deploy-artifact.tar.gz" -C '${{inputs.firebase-public-dir}}'
+        tar -xvzf "$extractDir/deploy-artifact.tar.gz" -C "$publicDir"
+
+        # Defense-in-depth: fail the deploy if the extracted artifact contains
+        # symlinks. The artifact is attacker-influenced (PR-supplied build
+        # output); a symlink such as `public/leak -> /proc/self/environ` or
+        # `public/leak -> ~/.config/gcloud/application_default_credentials.json`
+        # would otherwise be followed by downstream tooling that walks
+        # `firebase-public-dir` and reads each entry, ending up on the
+        # public Firebase Hosting CDN. There is no legitimate reason for a
+        # `public` artifact destined for static hosting to contain
+        # symlinks, so refusing them outright is the safest default.
+        # See https://securitylab.github.com/research/github-actions-preventing-pwn-requests/.
+        symlinks=$(find "$publicDir" -type l 2>/dev/null || true)
+        if [ -n "$symlinks" ]; then
+          echo "::error title=Symlinks rejected in artifact::The deploy artifact contains symlinks, which are not permitted in a Hosting public directory for security reasons (a symlink can leak the contents of files outside the source tree onto the public Firebase Hosting CDN)."
+          echo "Symlinks found:"
+          echo "$symlinks"
+          exit 1
+        fi
 
     - name: Extracting artifact metadata
       id: artifact-info