diff --git a/manifest.json b/manifest.json
index 87f4433..38f17c7 100644
--- a/manifest.json
+++ b/manifest.json
@@ -14,7 +14,7 @@
         "email": "pierre@kayou.io"
     },
     "requirements": {
-        "yunohost": ">= 4.2.0"
+        "yunohost": ">= 4.1.7"
     },
     "multi_instance": true,
     "services": [
diff --git a/scripts/_common.sh b/scripts/_common.sh
index 24bf200..3db6f6b 100644
--- a/scripts/_common.sh
+++ b/scripts/_common.sh
@@ -23,3 +23,49 @@ pkg_dependencies="git"
 # FUTURE OFFICIAL HELPERS
 #=================================================
 
+# Execute a command with Composer
+#
+# usage: ynh_composer_exec --phpversion=phpversion [--workdir=$final_path] --commands="commands"
+# | arg: -w, --workdir - The directory from where the command will be executed. Default $final_path.
+# | arg: -c, --commands - Commands to execute.
+ynh_composer_exec () {
+	# Declare an array to define the options of this helper.
+	local legacy_args=vwc
+	declare -Ar args_array=( [v]=phpversion= [w]=workdir= [c]=commands= )
+	local phpversion
+	local workdir
+	local commands
+	# Manage arguments with getopts
+	ynh_handle_getopts_args "$@"
+	workdir="${workdir:-$final_path}"
+	phpversion="${phpversion:-7.3}"
+
+	COMPOSER_HOME="$workdir/.composer" \
+		php${phpversion} "$workdir/composer.phar" $commands \
+		-d "$workdir" --quiet --no-interaction
+}
+
+# Install and initialize Composer in the given directory
+#
+# usage: ynh_install_composer --phpversion=phpversion [--workdir=$final_path]
+# | arg: -w, --workdir - The directory from where the command will be executed. Default $final_path.
+ynh_install_composer () {
+	# Declare an array to define the options of this helper.
+	local legacy_args=vw
+	declare -Ar args_array=( [v]=phpversion= [w]=workdir= )
+	local phpversion
+	local workdir
+	# Manage arguments with getopts
+	ynh_handle_getopts_args "$@"
+	workdir="${workdir:-$final_path}"
+	phpversion="${phpversion:-7.0}"
+
+	curl -sS https://getcomposer.org/installer \
+		| COMPOSER_HOME="$workdir/.composer" \
+		php${phpversion} -- --quiet --install-dir="$workdir" \
+		|| ynh_die "Unable to install Composer."
+
+	# update dependencies to create composer.lock
+	ynh_composer_exec --phpversion="${phpversion}" --workdir="$workdir" --commands="install --no-dev" \
+		|| ynh_die "Unable to update core dependencies with Composer."
+}
diff --git a/scripts/install b/scripts/install
index d031e15..941caec 100755
--- a/scripts/install
+++ b/scripts/install
@@ -63,14 +63,6 @@ ynh_script_progression --message="Installing dependencies..." --weight=5
 
 ynh_install_app_dependencies $pkg_dependencies
 
-#=================================================
-# CREATE DEDICATED USER
-#=================================================
-ynh_script_progression --message="Configuring system user..." --weight=2
-
-# Create a system user
-ynh_system_user_create --username=$app --home_dir="$final_path"
-
 #=================================================
 # DOWNLOAD, CHECK AND UNPACK SOURCE
 #=================================================
@@ -80,10 +72,6 @@ ynh_app_setting_set --app=$app --key=final_path --value=$final_path
 # Download, check integrity, uncompress and patch the source from app.src
 ynh_setup_source --dest_dir="$final_path"
 
-chmod 750 "$final_path"
-chmod -R o-rwx "$final_path"
-chown -R $app:www-data "$final_path"
-
 #=================================================
 # NGINX CONFIGURATION
 #=================================================
@@ -92,6 +80,14 @@ ynh_script_progression --message="Configuring NGINX web server..." --weight=1
 # Create a dedicated nginx config
 ynh_add_nginx_config
 
+#=================================================
+# CREATE DEDICATED USER
+#=================================================
+ynh_script_progression --message="Configuring system user..." --weight=2
+
+# Create a system user
+ynh_system_user_create --username=$app
+
 #=================================================
 # PHP-FPM CONFIGURATION
 #=================================================
@@ -120,6 +116,9 @@ mkdir -p "$final_path/sites/$domain"
 echo "{\"siteDomain\":\"$domain\",\"siteLabel\":\"$domain\",\"admins\":[],\"siteLang\":\"$language\",\
 \"siteDescription\":\"Site r\u00e9alis\u00e9 avec FramaSite\",\"siteKeywords\":\"\"}" > "$final_path/sites/$domain/config.json"
 
+# Set permissions to app files
+chown -R $app: $final_path
+
 #=================================================
 # SETUP APPLICATION WITH CURL
 #=================================================
diff --git a/scripts/restore b/scripts/restore
index 6bf84ec..b238d5e 100755
--- a/scripts/restore
+++ b/scripts/restore
@@ -50,14 +50,6 @@ test ! -d $final_path \
 
 ynh_restore_file --origin_path="/etc/nginx/conf.d/$domain.d/$app.conf"
 
-#=================================================
-# RECREATE THE DEDICATED USER
-#=================================================
-ynh_script_progression --message="Recreating the dedicated system user..." --weight=3
-
-# Create the dedicated user (if not existing)
-ynh_system_user_create --username=$app --home_dir="$final_path"
-
 #=================================================
 # RESTORE THE APP MAIN DIR
 #=================================================
@@ -65,9 +57,20 @@ ynh_script_progression --message="Restoring the app main directory..." --weight=
 
 ynh_restore_file --origin_path="$final_path"
 
-chmod 750 "$final_path"
-chmod -R o-rwx "$final_path"
-chown -R $app:www-data "$final_path"
+#=================================================
+# RECREATE THE DEDICATED USER
+#=================================================
+ynh_script_progression --message="Recreating the dedicated system user..." --weight=3
+
+# Create the dedicated user (if not existing)
+ynh_system_user_create --username=$app
+
+#=================================================
+# RESTORE USER RIGHTS
+#=================================================
+
+# Restore permissions on app files
+chown -R $app: $final_path
 
 #=================================================
 # RESTORE THE PHP-FPM CONFIGURATION
@@ -75,6 +78,7 @@ chown -R $app:www-data "$final_path"
 ynh_script_progression --message="Reconfiguring PHP-FPM..." --weight=2
 
 ynh_restore_file --origin_path="/etc/php/$phpversion/fpm/pool.d/$app.conf"
+
 ynh_add_fpm_config --package="$extra_php_dependencies"
 
 #=================================================
diff --git a/scripts/upgrade b/scripts/upgrade
index b540e77..ebbbbed 100755
--- a/scripts/upgrade
+++ b/scripts/upgrade
@@ -66,14 +66,6 @@ ynh_clean_setup () {
 # Exit if an error occurs during the execution of the script
 ynh_abort_if_errors
 
-#=================================================
-# CREATE DEDICATED USER
-#=================================================
-ynh_script_progression --message="Making sure dedicated system user exists..." --weight=1
-
-# Create a dedicated user (if not existing)
-ynh_system_user_create --username=$app --home_dir="$final_path"
-
 #=================================================
 # STANDARD UPGRADE STEPS
 #=================================================
@@ -88,10 +80,6 @@ then
 	ynh_setup_source --dest_dir="$final_path"
 fi
 
-chmod 750 "$final_path"
-chmod -R o-rwx "$final_path"
-chown -R $app:www-data "$final_path"
-
 #=================================================
 # NGINX CONFIGURATION
 #=================================================
@@ -107,6 +95,14 @@ ynh_script_progression --message="Upgrading dependencies..." --weight=5
 
 ynh_install_app_dependencies $pkg_dependencies
 
+#=================================================
+# CREATE DEDICATED USER
+#=================================================
+ynh_script_progression --message="Making sure dedicated system user exists..." --weight=1
+
+# Create a dedicated user (if not existing)
+ynh_system_user_create --username=$app
+
 #=================================================
 # PHP-FPM CONFIGURATION
 #=================================================
@@ -128,6 +124,15 @@ ynh_store_file_checksum --file="$final_path/sites/$domain/config.json"
 # Fix a bug where images can't be uploaded
 ynh_replace_string --match_string="isMediaPathModified = true" --replace_string="" --target_file="$final_path/app/config/config.ini"
 
+#=================================================
+# GENERIC FINALIZATION
+#=================================================
+# SECURE FILES AND DIRECTORIES
+#=================================================
+
+# Set permissions on app files
+chown -R $app: $final_path
+
 #=================================================
 # RELOAD NGINX
 #=================================================