diff --git a/packages/features/ee/integration-attribute-sync/repositories/IIntegrationAttributeSyncRepository.ts b/packages/features/ee/integration-attribute-sync/repositories/IIntegrationAttributeSyncRepository.ts
index fe571fa50b..af0ec8ba02 100644
--- a/packages/features/ee/integration-attribute-sync/repositories/IIntegrationAttributeSyncRepository.ts
+++ b/packages/features/ee/integration-attribute-sync/repositories/IIntegrationAttributeSyncRepository.ts
@@ -63,6 +63,7 @@ export interface ISyncFormData {
   id: string;
   name: string;
   credentialId?: number;
+  integration?: AttributeSyncIntegrations;
   enabled: boolean;
   organizationId: number;
   ruleId: string;
@@ -138,7 +139,7 @@ export interface IIntegrationAttributeSyncUpdateParams {
   integrationAttributeSync: Omit<
     IntegrationAttributeSync,
     "attributeSyncRule" | "syncFieldMappings" | "integration"
-  >;
+  > & { integration?: AttributeSyncIntegrations };
   attributeSyncRule: AttributeSyncRule;
   fieldMappingsToCreate: Omit<AttributeSyncFieldMapping, "id">[];
   fieldMappingsToUpdate: AttributeSyncFieldMapping[];
diff --git a/packages/features/ee/integration-attribute-sync/services/IntegrationAttributeSyncService.ts b/packages/features/ee/integration-attribute-sync/services/IntegrationAttributeSyncService.ts
index 3d3ce37133..50e7a1c4cb 100644
--- a/packages/features/ee/integration-attribute-sync/services/IntegrationAttributeSyncService.ts
+++ b/packages/features/ee/integration-attribute-sync/services/IntegrationAttributeSyncService.ts
@@ -217,4 +217,11 @@ export class IntegrationAttributeSyncService {
   async getAllByCredentialId(credentialId: number) {
     return this.deps.integrationAttributeSyncRepository.getAllByCredentialId(credentialId);
   }
+
+  async validateCredentialBelongsToOrg(credentialId: number, organizationId: number) {
+    return this.deps.credentialRepository.findByIdAndTeamId({
+      id: credentialId,
+      teamId: organizationId,
+    });
+  }
 }
diff --git a/packages/trpc/server/routers/viewer/attribute-sync/updateAttributeSync.handler.ts b/packages/trpc/server/routers/viewer/attribute-sync/updateAttributeSync.handler.ts
index 207fa6e480..1ff9b2e497 100644
--- a/packages/trpc/server/routers/viewer/attribute-sync/updateAttributeSync.handler.ts
+++ b/packages/trpc/server/routers/viewer/attribute-sync/updateAttributeSync.handler.ts
@@ -1,4 +1,8 @@
 import { getIntegrationAttributeSyncService } from "@calcom/ee/integration-attribute-sync/di/IntegrationAttributeSyncService.container";
+import {
+  AttributeSyncIntegrations,
+  type ISyncFormData,
+} from "@calcom/ee/integration-attribute-sync/repositories/IIntegrationAttributeSyncRepository";
 import {
   DuplicateAttributeWithinSyncError,
   DuplicateAttributeAcrossSyncsError,
@@ -37,8 +41,29 @@ const updateAttributeSyncHandler = async ({ ctx, input }: UpdateAttributeSyncOpt
     throw new TRPCError({ code: "UNAUTHORIZED" });
   }
 
+  // Never trust user-supplied organizationId — override with authenticated user's org
+  const safeInput: ISyncFormData = { ...input, organizationId: org.id };
+
+  // Validate credential belongs to the user's organization and derive integration type
+  if (input.credentialId !== undefined) {
+    const credential = await integrationAttributeSyncService.validateCredentialBelongsToOrg(
+      input.credentialId,
+      org.id
+    );
+    if (!credential) {
+      throw new TRPCError({ code: "NOT_FOUND", message: "Credential not found" });
+    }
+
+    const integrationValue = credential.app?.slug || credential.type;
+    if (!Object.values(AttributeSyncIntegrations).includes(integrationValue as AttributeSyncIntegrations)) {
+      throw new TRPCError({ code: "BAD_REQUEST", message: `Unsupported integration type: ${integrationValue}` });
+    }
+
+    safeInput.integration = integrationValue as AttributeSyncIntegrations;
+  }
+
   try {
-    await integrationAttributeSyncService.updateIncludeRulesAndMappings(input);
+    await integrationAttributeSyncService.updateIncludeRulesAndMappings(safeInput);
   } catch (error) {
     if (error instanceof DuplicateAttributeWithinSyncError) {
       throw new TRPCError({