diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 01a5ce1602..a24d32ca91 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -14,7 +14,7 @@ jobs:
       matrix:
         java: [11, 17]
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
     - uses: actions/setup-java@v2
       with:
         distribution: temurin
@@ -28,7 +28,7 @@ jobs:
     name: "units (8)"
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
     - uses: actions/setup-java@v3
       with:
         java-version: 8
@@ -48,7 +48,7 @@ jobs:
   windows:
     runs-on: windows-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
     - uses: actions/setup-java@v2
       with:
         distribution: temurin
@@ -63,7 +63,7 @@ jobs:
       matrix:
         java: [17]
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
     - uses: actions/setup-java@v2
       with:
         distribution: temurin
@@ -73,7 +73,7 @@ jobs:
   javadoc:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: actions/setup-java@v3
         with:
           distribution: temurin
@@ -85,7 +85,7 @@ jobs:
   lint:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
     - uses: actions/setup-java@v2
       with:
         distribution: temurin
@@ -97,7 +97,7 @@ jobs:
   clirr:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v3
+    - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
     - uses: actions/setup-java@v2
       with:
         distribution: temurin
diff --git a/.github/workflows/samples.yaml b/.github/workflows/samples.yaml
index 9b1fe1529e..f8455b2212 100644
--- a/.github/workflows/samples.yaml
+++ b/.github/workflows/samples.yaml
@@ -7,7 +7,7 @@ jobs:
   checkstyle:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: actions/setup-java@v1
         with:
           java-version: 8