diff --git a/backend/src/utils/sanitize.ts b/backend/src/utils/sanitize.ts
index 3e382415..9a0294da 100644
--- a/backend/src/utils/sanitize.ts
+++ b/backend/src/utils/sanitize.ts
@@ -59,6 +59,39 @@ const PORTAL_HIDDEN_CONTRACT_FIELDS = [
   'nextReviewDate', // Snooze-Workflow ist internes Cockpit-Feature
 ] as const;
 
+// User-eingabe String-Felder am Contract, die in der UI dargestellt werden.
+// Werden beim Read über stripHtml geschickt, damit Alt-Daten mit rohen
+// XSS-Payloads (vor Einführung von sanitizeContractBody) nicht mehr als
+// `<script>alert(...)</script>` in der Liste auftauchen. Neue Daten sind
+// schon beim Write gestrippt, aber doppelt hält besser.
+const CONTRACT_DISPLAY_STRING_FIELDS = [
+  'providerName',
+  'tariffName',
+  'customerNumberAtProvider',
+  'contractNumberAtProvider',
+  'portalUsername',
+  'previousProviderName',
+  'previousCustomerNumber',
+  'previousContractNumber',
+  'notes',
+] as const;
+
+// User-eingabe String-Felder am Customer für dieselbe Read-Time-Defensive.
+const CUSTOMER_DISPLAY_STRING_FIELDS = [
+  'firstName',
+  'lastName',
+  'companyName',
+  'salutation',
+  'email',
+  'phone',
+  'mobile',
+  'portalEmail',
+  'portalUsername',
+  'taxNumber',
+  'commercialRegisterNumber',
+  'notes',
+] as const;
+
 const SENSITIVE_USER_FIELDS = [
   'password',
   'passwordResetToken',
@@ -79,6 +112,11 @@ export function sanitizeCustomer<T extends Record<string, unknown>>(customer: T
   for (const field of SENSITIVE_CUSTOMER_FIELDS) {
     delete copy[field];
   }
+  for (const field of CUSTOMER_DISPLAY_STRING_FIELDS) {
+    if (typeof copy[field] === 'string') {
+      copy[field] = stripHtml(copy[field]);
+    }
+  }
   if (Array.isArray(copy.contracts)) {
     copy.contracts = (copy.contracts as Record<string, unknown>[]).map((c) => sanitizeContract(c));
   }
@@ -126,6 +164,25 @@ export function sanitizeContract<T extends Record<string, unknown>>(contract: T
   for (const field of SENSITIVE_CONTRACT_FIELDS) {
     delete copy[field];
   }
+  for (const field of CONTRACT_DISPLAY_STRING_FIELDS) {
+    if (typeof copy[field] === 'string') {
+      copy[field] = stripHtml(copy[field]);
+    }
+  }
+  // Nested: previousProviderName liegt im energyDetails-Sub-Objekt
+  if (copy.energyDetails && typeof copy.energyDetails === 'object') {
+    const ed = copy.energyDetails as Record<string, unknown>;
+    if (typeof ed.previousProviderName === 'string') {
+      ed.previousProviderName = stripHtml(ed.previousProviderName);
+    }
+    if (typeof ed.previousCustomerNumber === 'string') {
+      ed.previousCustomerNumber = stripHtml(ed.previousCustomerNumber);
+    }
+  }
+  // Nested: previousContract wird rekursiv auch sanitisiert
+  if (copy.previousContract && typeof copy.previousContract === 'object') {
+    copy.previousContract = sanitizeContract(copy.previousContract as Record<string, unknown>);
+  }
   if (copy.customer && typeof copy.customer === 'object') {
     copy.customer = sanitizeCustomer(copy.customer as Record<string, unknown>);
   }