diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f3383b7..0611019 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -24,8 +24,8 @@ jobs:
           - integrationTestMounts
           - integrationTestXenitEndpoints
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-java@v1
+      - uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2
+      - uses: actions/setup-java@b6e674f4b717d7b0ae3baee0fbe79f498905dfde # v1
         with:
           java-version: 1.11
       - name: install docker-compose
@@ -47,7 +47,7 @@ jobs:
           arguments: ${{ matrix.task }} --info
       - name: Upload Artifact
         if: success() || failure()
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@9ee08a3b00e91a926cc9547dc79589c20872452f # v3
         with:
           name: ${{ matrix.task }}-result
           path: /home/runner/work/**/build/reports
@@ -61,9 +61,9 @@ jobs:
         version:
           - solr6
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@ee0669bd1cc54295c223e0bb666b733df41de1c5 # v2
       - name: Setup Gradle
-        uses: gradle/gradle-build-action@v2
+        uses: gradle/gradle-build-action@a8f75513eafdebd8141bd1cd4e30fcd194af8dfa # v2
       - name: Login to CloudSmith
         run: |
           echo "${{ secrets.CLOUDSMITH_APIKEY }}" | docker login private.docker.xenit.eu --username "${{ secrets.CLOUDSMITH_USER }}" --password-stdin
diff --git a/src/integrationTest/resources/docker-compose-db.yml b/src/integrationTest/resources/docker-compose-db.yml
index e938268..85c37b2 100644
--- a/src/integrationTest/resources/docker-compose-db.yml
+++ b/src/integrationTest/resources/docker-compose-db.yml
@@ -2,7 +2,7 @@ version: '3'
 
 services:
  postgresql:
-   image: docker.io/xenit/postgres
+   image: docker.io/xenit/postgres@sha256:d9c3e2a7c41c668835adb8752b17ad1506dcd38744a0c67ca90699a7be4b7e80
    environment:
    - POSTGRES_USER=alfresco
    - POSTGRES_PASSWORD=admin
diff --git a/src/main/resources/dockerfiles/Dockerfile.solr6 b/src/main/resources/dockerfiles/Dockerfile.solr6
index e569875..176feb5 100644
--- a/src/main/resources/dockerfiles/Dockerfile.solr6
+++ b/src/main/resources/dockerfiles/Dockerfile.solr6
@@ -1,5 +1,5 @@
-ARG BASE_IMAGE=docker.io/xenit/openjdk:alfresco-6.1-ubuntu
-FROM	alpine:latest AS build-stage-solr6
+ARG BASE_IMAGE=docker.io/xenit/openjdk:alfresco-6.1-ubuntu@sha256:d49df9fb6638b816e979445cff3997122b63a7a81c1864788827ac6ad1964d37
+FROM	alpine:latest@sha256:0a4eaa0eecf5f8c050e5bba433f58c052be7587ee8af3e8b3910ef9ab5fbe9f5 AS build-stage-solr6
 
 ARG SOLR_VERSION_MAJOR
 ARG SOLR_VERSION_MINOR