diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
index 3f35630..a7827d9 100644
--- a/.github/workflows/deploy.yml
+++ b/.github/workflows/deploy.yml
@@ -23,11 +23,11 @@ jobs:
       pages: write
       id-token: write
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
 
       # Install dependencies
       - name: Set up Python 3.11
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065 # v5
         with:
           python-version: 3.11
           cache: 'pip' # cache pip dependencies
@@ -43,11 +43,11 @@ jobs:
 
       # Upload the book's HTML as an artifact
       - name: Upload artifact
-        uses: actions/upload-pages-artifact@v3
+        uses: actions/upload-pages-artifact@56afc609e74202658d3ffba0e8f6dda462b719fa # v3
         with:
           path: "book/_build/html"
 
       # Deploy the book's HTML to GitHub Pages
       - name: Deploy to GitHub Pages
         id: deployment
-        uses: actions/deploy-pages@v4
+        uses: actions/deploy-pages@d6db90164ac5ed86f2b6aed7e0febac5b3c0c03e # v4