diff --git a/.github/workflows/format_php.yml b/.github/workflows/format_php.yml
index 0989951..bae8ce8 100644
--- a/.github/workflows/format_php.yml
+++ b/.github/workflows/format_php.yml
@@ -14,12 +14,12 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 7
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
         with:
           ref: ${{ github.head_ref }}
 
       - name: Setup PHP
-        uses: shivammathur/setup-php@v2
+        uses: shivammathur/setup-php@7c071dfe9dc99bdf297fa79cb49ea005b9fcadbc # v2
         with:
           php-version: 8.4
           coverage: none
@@ -30,7 +30,7 @@ jobs:
           echo "composer_dir={$(composer config cache-files-dir)}" >> $GITHUB_OUTPUT
 
       - name: Retrieve Composer‘s cache
-        uses: actions/cache@v5
+        uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5
         with:
           path: ${{ steps.composer-cache.outputs.composer_dir }}
           key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.json') }}
@@ -41,7 +41,7 @@ jobs:
         run: "composer install --no-interaction --no-progress --no-scripts"
 
       - name: Retrieve PHPCS‘s cache
-        uses: actions/cache@v5
+        uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5
         with:
           path: .cache/phpcs
           key: ${{ runner.os }}-phpcs-${{ hashFiles('phpcs.xml') }}
diff --git a/.github/workflows/psalm.yml b/.github/workflows/psalm.yml
index ebb233f..52da825 100644
--- a/.github/workflows/psalm.yml
+++ b/.github/workflows/psalm.yml
@@ -16,16 +16,16 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 5
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
         with:
           ref: ${{ github.head_ref }}
 
       # mtime needs to be restored for Psalm cache to work correctly
       - name: Restore mtimes
-        uses: chetan/git-restore-mtime-action@v2
+        uses: chetan/git-restore-mtime-action@d186aca54f8760da4dec55313195e51ed3ebb0b3 # v2
 
       - name: Setup PHP
-        uses: shivammathur/setup-php@v2
+        uses: shivammathur/setup-php@7c071dfe9dc99bdf297fa79cb49ea005b9fcadbc # v2
         with:
           php-version: 8.4
           coverage: none
@@ -36,7 +36,7 @@ jobs:
           echo "composer_dir={$(composer config cache-files-dir)}" >> $GITHUB_OUTPUT
 
       - name: Retrieve Composer‘s cache
-        uses: actions/cache@v5
+        uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5
         with:
           path: ${{ steps.composer-cache.outputs.composer_dir }}
           key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
@@ -49,7 +49,7 @@ jobs:
       # the way cache keys are set up will always cause a cache miss
       # but will restore the cache generated during the previous run based on partial match
       - name: Retrieve Psalm’s cache
-        uses: actions/cache@v5
+        uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5
         with:
           path: ./cache/psalm
           key: ${{ runner.os }}-psalm-cache-${{ hashFiles('psalm.xml', 'psalm-baseline.xml') }}
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 17cece4..f5ea83a 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -33,10 +33,10 @@ jobs:
 
     steps:
       - name: "Checkout"
-        uses: "actions/checkout@v6"
+        uses: "actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd" # v6
 
       - name: "Install PHP"
-        uses: "shivammathur/setup-php@v2"
+        uses: "shivammathur/setup-php@7c071dfe9dc99bdf297fa79cb49ea005b9fcadbc" # v2
         with:
           coverage: "none"
           php-version: "${{ matrix.php-version }}"
diff --git a/.github/workflows/validator.yml b/.github/workflows/validator.yml
index 1bc0fad..0dc394d 100644
--- a/.github/workflows/validator.yml
+++ b/.github/workflows/validator.yml
@@ -13,12 +13,12 @@ jobs:
     runs-on: ubuntu-latest
     timeout-minutes: 5
     steps:
-      - uses: actions/checkout@v6
+      - uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6
         with:
           ref: ${{ github.head_ref }}
 
       - name: Setup PHP
-        uses: shivammathur/setup-php@v2
+        uses: shivammathur/setup-php@7c071dfe9dc99bdf297fa79cb49ea005b9fcadbc # v2
         with:
           php-version: 8.4
           coverage: none
@@ -29,7 +29,7 @@ jobs:
           echo "composer_dir={$(composer config cache-files-dir)}" >> $GITHUB_OUTPUT
 
       - name: Retrieve Composer‘s cache
-        uses: actions/cache@v5
+        uses: actions/cache@27d5ce7f107fe9357f9df03efb73ab90386fccae # v5
         with:
           path: ${{ steps.composer-cache.outputs.composer_dir }}
           key: ${{ runner.os }}-composer-${{ hashFiles('**/composer.lock') }}
@@ -40,6 +40,6 @@ jobs:
         run: "composer install --no-interaction --no-progress --no-scripts"
 
       - name: Validate ruleset
-        uses: szepeviktor/phpcs-ruleset-validator@v0.4.0
+        uses: szepeviktor/phpcs-ruleset-validator@f07738521ac7d7dd31ccec1920022e6fae617bcb # v0.4.0
         with:
           xml_ruleset: IxDFCodingStandard/ruleset.xml