diff --git a/CHANGELOG.md b/CHANGELOG.md
index fbb3bdcc97..f04aa58104 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -21,6 +21,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Fixed the border color of the drop area in the import activities dialog (dark mode)
 - Fixed the matching of assets and accounts in the import of activities with _Ghostfolio AI_ (experimental)
+- Fixed an issue where the update of an activity could change the asset class and asset sub class of an asset profile which does not belong to the user
 
 ## 3.84.2 - 2026-10-11
 
diff --git a/apps/api/src/app/activities/activities.service.spec.ts b/apps/api/src/app/activities/activities.service.spec.ts
index fb2c68ff40..57bd8ab665 100644
--- a/apps/api/src/app/activities/activities.service.spec.ts
+++ b/apps/api/src/app/activities/activities.service.spec.ts
@@ -18,7 +18,9 @@ import { Activity, Filter } from '@ghostfolio/common/interfaces';
 
 import { EventEmitter2 } from '@nestjs/event-emitter';
 import {
+  AssetClass,
   AssetProfileSplit,
+  AssetSubClass,
   DataSource,
   Prisma,
   Type as ActivityType
@@ -519,6 +521,105 @@ describe('ActivitiesService', () => {
       });
     });
   });
+
+  describe('updateActivity', () => {
+    it('updates the custom asset profile of the user', async () => {
+      const data = await getUpdatedActivityData({ userId: 'user-id' });
+
+      expect(data.SymbolProfile).toEqual({
+        update: {
+          data: {
+            assetClass: AssetClass.COMMODITY,
+            assetSubClass: AssetSubClass.PRECIOUS_METAL
+          },
+          where: { userId: 'user-id' }
+        }
+      });
+    });
+
+    it.each([
+      { owner: 'the admin', userId: null },
+      { owner: 'another user', userId: 'other-user-id' }
+    ])('does not update the asset profile of $owner', async ({ userId }) => {
+      const data = await getUpdatedActivityData({ userId });
+
+      expect(data).not.toHaveProperty('SymbolProfile');
+    });
+
+    it('does not update the asset profile of a data provider', async () => {
+      const data = await getUpdatedActivityData({
+        dataSource: DataSource.YAHOO,
+        symbol: 'AAPL',
+        type: ActivityType.FEE,
+        userId: null
+      });
+
+      expect(data).not.toHaveProperty('SymbolProfile');
+    });
+
+    async function getUpdatedActivityData({
+      dataSource = DataSource.MANUAL,
+      symbol = 'GF_GOLD',
+      type = ActivityType.BUY,
+      userId
+    }: {
+      dataSource?: DataSource;
+      symbol?: string;
+      type?: ActivityType;
+      userId: string | null;
+    }) {
+      const update = jest.fn().mockResolvedValue({ userId: 'user-id' });
+
+      const service = new ActivitiesService(
+        null,
+        null,
+        null,
+        null,
+        null,
+        null,
+        { emit: jest.fn() } as unknown as EventEmitter2,
+        null,
+        null,
+        {
+          order: {
+            update,
+            findUnique: jest
+              .fn()
+              .mockResolvedValue({ SymbolProfile: { userId } })
+          }
+        } as unknown as PrismaService,
+        null,
+        { validateTagIds: jest.fn() } as unknown as TagService
+      );
+
+      await service.updateActivity({
+        data: {
+          type,
+          assetClass: AssetClass.COMMODITY,
+          assetSubClass: AssetSubClass.PRECIOUS_METAL,
+          date: parseDate('2024-01-01'),
+          SymbolProfile: {
+            connect: {
+              dataSource_symbol: {
+                dataSource,
+                symbol
+              }
+            },
+            update: {
+              assetClass: AssetClass.COMMODITY,
+              assetSubClass: AssetSubClass.PRECIOUS_METAL,
+              name: symbol
+            }
+          }
+        },
+        originalDate: parseDate('2024-01-01'),
+        userId: 'user-id',
+        where: { id: 'activity-id' }
+      });
+
+      return (update.mock.calls[0] as [Prisma.OrderUpdateArgs])[0].data;
+    }
+  });
 });
 
 function createActivity({
diff --git a/apps/api/src/app/activities/activities.service.ts b/apps/api/src/app/activities/activities.service.ts
index 0de3f7c3c4..0dce736f4e 100644
--- a/apps/api/src/app/activities/activities.service.ts
+++ b/apps/api/src/app/activities/activities.service.ts
@@ -933,7 +933,23 @@ export class ActivitiesService {
         data.type === 'BUY')
     ) {
       delete data.SymbolProfile.connect;
-      delete data.SymbolProfile.update.name;
+
+      const activityToUpdate = await this.prismaService.order.findUnique({
+        select: { SymbolProfile: { select: { userId: true } } },
+        where
+      });
+
+      if (activityToUpdate?.SymbolProfile.userId === userId) {
+        data.SymbolProfile.update = {
+          data: {
+            assetClass: data.assetClass,
+            assetSubClass: data.assetSubClass
+          },
+          where: { userId }
+        };
+      } else {
+        delete data.SymbolProfile;
+      }
     } else {
       delete data.SymbolProfile.update;