2 files changed, 6 insertions, 4 deletions

diff --git a/server/middlewares/validators/config.ts b/server/middlewares/validators/config.ts
index 31b131914..9c43da165 100644
--- a/server/middlewares/validators/config.ts
+++ b/server/middlewares/validators/config.ts
@@ -5,7 +5,8 @@ import { logger } from '../../helpers/logger'
 import { CustomConfig } from '../../../shared/models/server/custom-config.model'
 import { Emailer } from '../../lib/emailer'
 import { areValidationErrors } from './utils'
-import { isThemeValid } from '../../helpers/custom-validators/plugins'
+import { isThemeNameValid } from '../../helpers/custom-validators/plugins'
+import { isThemeRegistered } from '../../lib/plugins/theme-utils'
 
 const customConfigUpdateValidator = [
   body('instance.name').exists().withMessage('Should have a valid instance name'),
@@ -48,7 +49,7 @@ const customConfigUpdateValidator = [
   body('followers.instance.enabled').isBoolean().withMessage('Should have a valid followers of instance boolean'),
   body('followers.instance.manualApproval').isBoolean().withMessage('Should have a valid manual approval boolean'),
 
-  body('theme.default').custom(isThemeValid).withMessage('Should have a valid theme'),
+  body('theme.default').custom(v => isThemeNameValid(v) && isThemeRegistered(v)).withMessage('Should have a valid theme'),
 
   async (req: express.Request, res: express.Response, next: express.NextFunction) => {
     logger.debug('Checking customConfigUpdateValidator parameters', { parameters: req.body })
diff --git a/server/middlewares/validators/users.ts b/server/middlewares/validators/users.ts
index df7f77b84..a507afc5b 100644
--- a/server/middlewares/validators/users.ts
+++ b/server/middlewares/validators/users.ts
@@ -28,7 +28,8 @@ import { ActorModel } from '../../models/activitypub/actor'
 import { isActorPreferredUsernameValid } from '../../helpers/custom-validators/activitypub/actor'
 import { isVideoChannelNameValid } from '../../helpers/custom-validators/video-channels'
 import { UserRegister } from '../../../shared/models/users/user-register.model'
-import { isThemeValid } from '../../helpers/custom-validators/plugins'
+import { isThemeNameValid } from '../../helpers/custom-validators/plugins'
+import { isThemeRegistered } from '../../lib/plugins/theme-utils'
 
 const usersAddValidator = [
   body('username').custom(isUserUsernameValid).withMessage('Should have a valid username (lowercase alphanumeric characters)'),
@@ -207,7 +208,7 @@ const usersUpdateMeValidator = [
     .custom(isUserVideosHistoryEnabledValid).withMessage('Should have a valid videos history enabled attribute'),
   body('theme')
     .optional()
-    .custom(isThemeValid).withMessage('Should have a valid theme'),
+    .custom(v => isThemeNameValid(v) && isThemeRegistered(v)).withMessage('Should have a valid theme'),
 
   async (req: express.Request, res: express.Response, next: express.NextFunction) => {
     logger.debug('Checking usersUpdateMe parameters', { parameters: omit(req.body, 'password') })