diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index a0e2bd033a..9e8e898b3d 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -65,8 +65,13 @@ jobs:
         uses: niden/actions-memcached@v7
 
       - name: Install dependencies.
+        if: matrix.php != '8.4'
         run: composer update $DEFAULT_COMPOSER_FLAGS
 
+      - name: Install dependencies with PHP 8.4.
+        if: matrix.php == '8.4'
+        run: composer update $DEFAULT_COMPOSER_FLAGS --ignore-platform-reqs
+
       - name: Run tests with PHPUnit and generate coverage.
         if: matrix.php == '7.4'
         run: vendor/bin/phpunit --verbose --exclude-group $PHPUNIT_EXCLUDE_GROUP --coverage-clover=coverage.xml --colors=always
diff --git a/.github/workflows/ci-mssql.yml b/.github/workflows/ci-mssql.yml
index 698cf61304..5ed0abcb76 100644
--- a/.github/workflows/ci-mssql.yml
+++ b/.github/workflows/ci-mssql.yml
@@ -66,8 +66,13 @@ jobs:
         run: composer self-update
 
       - name: Install dependencies with composer
+        if: matrix.php != '8.4'
         run: composer update --prefer-dist --no-interaction --no-progress --optimize-autoloader --ansi
 
+      - name: Install dependencies with PHP 8.4.
+        if: matrix.php == '8.4'
+        run: composer update --prefer-dist --no-interaction --no-progress --optimize-autoloader --ignore-platform-reqs --ansi
+
       - name: Run MSSQL tests with PHPUnit and generate coverage.
         run: vendor/bin/phpunit --group mssql --coverage-clover=coverage.xml --colors=always
 
diff --git a/.github/workflows/ci-mysql.yml b/.github/workflows/ci-mysql.yml
index 7bec235224..5753d91695 100644
--- a/.github/workflows/ci-mysql.yml
+++ b/.github/workflows/ci-mysql.yml
@@ -47,9 +47,14 @@ jobs:
           php-version: ${{ matrix.php }}
           tools: composer:v2, pecl
 
-      - name: Install dependencies with composer.
+      - name: Install dependencies with composer
+        if: matrix.php != '8.4'
         run: composer update --prefer-dist --no-interaction --no-progress --optimize-autoloader --ansi
 
+      - name: Install dependencies with PHP 8.4.
+        if: matrix.php == '8.4'
+        run: composer update --prefer-dist --no-interaction --no-progress --optimize-autoloader --ignore-platform-reqs --ansi
+
       - name: Run MySQL tests with PHPUnit and generate coverage.
         run: vendor/bin/phpunit --group mysql --coverage-clover=coverage.xml --colors=always
 
diff --git a/.github/workflows/ci-pgsql.yml b/.github/workflows/ci-pgsql.yml
index 8dd8b3d6da..4b926645b8 100644
--- a/.github/workflows/ci-pgsql.yml
+++ b/.github/workflows/ci-pgsql.yml
@@ -51,9 +51,14 @@ jobs:
       - name: Update composer.
         run: composer self-update
 
-      - name: Install dependencies with composer.
+      - name: Install dependencies with composer
+        if: matrix.php != '8.4'
         run: composer update --prefer-dist --no-interaction --no-progress --optimize-autoloader --ansi
 
+      - name: Install dependencies with PHP 8.4.
+        if: matrix.php == '8.4'
+        run: composer update --prefer-dist --no-interaction --no-progress --optimize-autoloader --ignore-platform-reqs --ansi
+
       - name: Run Pgsql tests with PHPUnit and generate coverage.
         run: vendor/bin/phpunit --group pgsql --coverage-clover=coverage.xml --colors=always
 
diff --git a/.github/workflows/ci-sqlite.yml b/.github/workflows/ci-sqlite.yml
index bf53dc3597..fe7405ea4e 100644
--- a/.github/workflows/ci-sqlite.yml
+++ b/.github/workflows/ci-sqlite.yml
@@ -40,9 +40,14 @@ jobs:
       - name: Update composer.
         run: composer self-update
 
-      - name: Install dependencies with composer.
+      - name: Install dependencies with composer
+        if: matrix.php != '8.4'
         run: composer update --prefer-dist --no-interaction --no-progress --optimize-autoloader --ansi
 
+      - name: Install dependencies with PHP 8.4.
+        if: matrix.php == '8.4'
+        run: composer update --prefer-dist --no-interaction --no-progress --optimize-autoloader --ignore-platform-reqs --ansi
+
       - name: Run SQLite tests with PHPUnit and generate coverage.
         run: vendor/bin/phpunit --group sqlite --coverage-clover=coverage.xml --colors=always
 
diff --git a/composer.json b/composer.json
index 90dc272071..af172dbb76 100644
--- a/composer.json
+++ b/composer.json
@@ -73,7 +73,7 @@
         "ext-ctype": "*",
         "lib-pcre": "*",
         "yiisoft/yii2-composer": "~2.0.4",
-        "ezyang/htmlpurifier": "^4.6",
+        "ezyang/htmlpurifier": "^4.17",
         "cebe/markdown": "~1.0.0 | ~1.1.0 | ~1.2.0",
         "bower-asset/jquery": "3.7.*@stable | 3.6.*@stable | 3.5.*@stable | 3.4.*@stable | 3.3.*@stable | 3.2.*@stable | 3.1.*@stable | 2.2.*@stable | 2.1.*@stable | 1.11.*@stable | 1.12.*@stable",
         "bower-asset/inputmask": "^5.0.8 ",
diff --git a/framework/composer.json b/framework/composer.json
index 37c438afb1..d24703fb44 100644
--- a/framework/composer.json
+++ b/framework/composer.json
@@ -68,7 +68,7 @@
         "ext-ctype": "*",
         "lib-pcre": "*",
         "yiisoft/yii2-composer": "~2.0.4",
-        "ezyang/htmlpurifier": "^4.6",
+        "ezyang/htmlpurifier": "^4.17",
         "cebe/markdown": "~1.0.0 | ~1.1.0 | ~1.2.0",
         "bower-asset/jquery": "3.7.*@stable | 3.6.*@stable | 3.5.*@stable | 3.4.*@stable | 3.3.*@stable | 3.2.*@stable | 3.1.*@stable | 2.2.*@stable | 2.1.*@stable | 1.11.*@stable | 1.12.*@stable",
         "bower-asset/inputmask": "^5.0.8 ",