diff --git a/fly/lib/common.sh b/fly/lib/common.sh
index 011bd644..ca281b1d 100644
--- a/fly/lib/common.sh
+++ b/fly/lib/common.sh
@@ -164,8 +164,16 @@ _fly_create_app() {
     local org
     org=$(get_fly_org)
 
+    # SECURITY: Validate org slug to prevent JSON injection via FLY_ORG env var
+    if [[ ! "$org" =~ ^[a-zA-Z0-9_-]+$ ]]; then
+        log_error "Invalid FLY_ORG: must be alphanumeric with hyphens/underscores only"
+        return 1
+    fi
+
     log_warn "Creating Fly.io app '$name'..."
-    local app_body="{\"app_name\":\"$name\",\"org_slug\":\"$org\"}"
+    # SECURITY: Use json_escape to prevent JSON injection
+    local app_body
+    app_body=$(printf '{"app_name":%s,"org_slug":%s}' "$(json_escape "$name")" "$(json_escape "$org")")
     local app_response
     app_response=$(fly_api POST "/apps" "$app_body")
 
@@ -197,18 +205,19 @@ _fly_create_machine() {
 
     log_warn "Creating Fly.io machine (region: $region, memory: ${vm_memory}MB)..."
 
+    # SECURITY: Pass values via environment variables to prevent Python injection
     local machine_body
-    machine_body=$(python3 -c "
-import json
+    machine_body=$(_FLY_NAME="$name" _FLY_REGION="$region" _FLY_MEM="$vm_memory" python3 -c "
+import json, os
 body = {
-    'name': '$name',
-    'region': '$region',
+    'name': os.environ['_FLY_NAME'],
+    'region': os.environ['_FLY_REGION'],
     'config': {
         'image': 'ubuntu:24.04',
         'guest': {
             'cpu_kind': 'shared',
             'cpus': 1,
-            'memory_mb': $vm_memory
+            'memory_mb': int(os.environ['_FLY_MEM'])
         },
         'init': {
             'exec': ['/bin/sleep', 'inf']
diff --git a/github-codespaces/lib/common.sh b/github-codespaces/lib/common.sh
index 9fe0ca53..628a98f4 100755
--- a/github-codespaces/lib/common.sh
+++ b/github-codespaces/lib/common.sh
@@ -195,6 +195,7 @@ upload_file() {
 }
 
 # Run a command on the codespace (wrapper matching other providers' interface)
+# SECURITY: Uses printf %q to properly escape commands to prevent injection
 run_server() {
     local cmd="$1"
 
@@ -203,7 +204,9 @@ run_server() {
         return 1
     fi
 
-    gh codespace ssh --codespace "$CODESPACE_NAME" -- bash -c "$cmd"
+    local escaped_cmd
+    escaped_cmd=$(printf '%q' "$cmd")
+    gh codespace ssh --codespace "$CODESPACE_NAME" -- bash -c "$escaped_cmd"
 }
 
 # Inject environment variables into shell config
diff --git a/koyeb/lib/common.sh b/koyeb/lib/common.sh
index 766e0feb..2315c732 100644
--- a/koyeb/lib/common.sh
+++ b/koyeb/lib/common.sh
@@ -201,6 +201,7 @@ create_server() {
 }
 
 # Run a command on the Koyeb service instance
+# SECURITY: Uses printf %q to properly escape commands to prevent injection
 run_server() {
     local cmd="$1"
 
@@ -209,7 +210,9 @@ run_server() {
         return 1
     fi
 
-    koyeb instances exec "$KOYEB_INSTANCE_ID" -- bash -c "$cmd"
+    local escaped_cmd
+    escaped_cmd=$(printf '%q' "$cmd")
+    koyeb instances exec "$KOYEB_INSTANCE_ID" -- bash -c "$escaped_cmd"
 }
 
 # Upload a file to the Koyeb instance via base64 encoding
@@ -278,7 +281,10 @@ interactive_session() {
     fi
 
     log_info "Starting interactive session..."
-    koyeb instances exec "$KOYEB_INSTANCE_ID" -- bash -c "$launch_cmd"
+    # SECURITY: Properly escape command to prevent injection
+    local escaped_cmd
+    escaped_cmd=$(printf '%q' "$launch_cmd")
+    koyeb instances exec "$KOYEB_INSTANCE_ID" -- bash -c "$escaped_cmd"
 }
 
 # Cleanup: delete the service and app
diff --git a/railway/lib/common.sh b/railway/lib/common.sh
index 673dd872..daa7f404 100644
--- a/railway/lib/common.sh
+++ b/railway/lib/common.sh
@@ -164,11 +164,14 @@ create_server() {
 }
 
 # Run a command on the Railway service
+# SECURITY: Uses printf %q to properly escape commands to prevent injection
 run_server() {
     local cmd="$1"
 
     # Railway CLI doesn't have a direct exec - we use shell command via railway run
-    railway run bash -c "$cmd"
+    local escaped_cmd
+    escaped_cmd=$(printf '%q' "$cmd")
+    railway run bash -c "$escaped_cmd"
 }
 
 # Upload a file to the Railway service
diff --git a/render/lib/common.sh b/render/lib/common.sh
index 27952435..e359a17b 100644
--- a/render/lib/common.sh
+++ b/render/lib/common.sh
@@ -183,6 +183,7 @@ create_server() {
 }
 
 # Run a command on the Render service via SSH
+# SECURITY: Uses printf %q to properly escape commands to prevent injection
 run_server() {
     local cmd="$1"
 
@@ -191,7 +192,9 @@ run_server() {
         return 1
     fi
 
-    render ssh --service "$RENDER_SERVICE_ID" -- bash -c "$cmd"
+    local escaped_cmd
+    escaped_cmd=$(printf '%q' "$cmd")
+    render ssh --service "$RENDER_SERVICE_ID" -- bash -c "$escaped_cmd"
 }
 
 # Upload a file to the Render service via base64 encoding over SSH
@@ -253,7 +256,10 @@ interactive_session() {
     fi
 
     log_info "Starting interactive session..."
-    render ssh --service "$RENDER_SERVICE_ID" -- bash -c "$launch_cmd"
+    # SECURITY: Properly escape command to prevent injection
+    local escaped_cmd
+    escaped_cmd=$(printf '%q' "$launch_cmd")
+    render ssh --service "$RENDER_SERVICE_ID" -- bash -c "$escaped_cmd"
 }
 
 # Cleanup: delete the service
diff --git a/shared/common.sh b/shared/common.sh
index 66edc705..e39e65b5 100644
--- a/shared/common.sh
+++ b/shared/common.sh
@@ -506,10 +506,14 @@ wait_for_oauth_code() {
 exchange_oauth_code() {
     local oauth_code="${1}"
 
+    # SECURITY: Use json_escape to prevent JSON injection via crafted OAuth codes
+    local escaped_code
+    escaped_code=$(json_escape "${oauth_code}")
+
     local key_response
     key_response=$(curl -s --max-time 30 -X POST "https://openrouter.ai/api/v1/auth/keys" \
         -H "Content-Type: application/json" \
-        -d "{\"code\": \"${oauth_code}\"}")
+        -d "{\"code\": ${escaped_code}}")
 
     local api_key
     api_key=$(echo "${key_response}" | grep -o '"key":"[^"]*"' | sed 's/"key":"//;s/"$//')