diff --git a/CHANGELOG.md b/CHANGELOG.md
index cc76998202..702996027e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -32,7 +32,7 @@ GET requests. (Issue [#1517](https://github.com/realm/realm-kotlin/pull/1517))
 * Minimum Android SDK: 16.
 
 ### Internal
-* None.
+* Updated to Realm Core 13.23.0, commit f8604b9fd3d2982008a1d3f5ff35e52ee9098d5b.
 
 
 ## 1.11.1 (2023-09-07)
diff --git a/packages/cinterop/src/commonMain/kotlin/io/realm/kotlin/internal/interop/RealmInterop.kt b/packages/cinterop/src/commonMain/kotlin/io/realm/kotlin/internal/interop/RealmInterop.kt
index 1cd6c153c9..293190fe4d 100644
--- a/packages/cinterop/src/commonMain/kotlin/io/realm/kotlin/internal/interop/RealmInterop.kt
+++ b/packages/cinterop/src/commonMain/kotlin/io/realm/kotlin/internal/interop/RealmInterop.kt
@@ -534,7 +534,6 @@ expect object RealmInterop {
     // User
     fun realm_user_get_all_identities(user: RealmUserPointer): List<SyncUserIdentity>
     fun realm_user_get_identity(user: RealmUserPointer): String
-    fun realm_user_get_auth_provider(user: RealmUserPointer): AuthProvider
     fun realm_user_get_access_token(user: RealmUserPointer): String
     fun realm_user_get_refresh_token(user: RealmUserPointer): String
     fun realm_user_get_device_id(user: RealmUserPointer): String
diff --git a/packages/cinterop/src/jvm/kotlin/io/realm/kotlin/internal/interop/RealmInterop.kt b/packages/cinterop/src/jvm/kotlin/io/realm/kotlin/internal/interop/RealmInterop.kt
index c2b2a07d8f..cd48ae8854 100644
--- a/packages/cinterop/src/jvm/kotlin/io/realm/kotlin/internal/interop/RealmInterop.kt
+++ b/packages/cinterop/src/jvm/kotlin/io/realm/kotlin/internal/interop/RealmInterop.kt
@@ -1114,10 +1114,6 @@ actual object RealmInterop {
         return realmc.realm_user_get_identity(user.cptr())
     }
 
-    actual fun realm_user_get_auth_provider(user: RealmUserPointer): AuthProvider {
-        return AuthProvider.of(realmc.realm_user_get_auth_provider(user.cptr()))
-    }
-
     actual fun realm_user_get_access_token(user: RealmUserPointer): String {
         return realmc.realm_user_get_access_token(user.cptr())
     }
diff --git a/packages/cinterop/src/nativeDarwin/kotlin/io/realm/kotlin/internal/interop/RealmInterop.kt b/packages/cinterop/src/nativeDarwin/kotlin/io/realm/kotlin/internal/interop/RealmInterop.kt
index 46facf20d2..54feccf235 100644
--- a/packages/cinterop/src/nativeDarwin/kotlin/io/realm/kotlin/internal/interop/RealmInterop.kt
+++ b/packages/cinterop/src/nativeDarwin/kotlin/io/realm/kotlin/internal/interop/RealmInterop.kt
@@ -2287,10 +2287,6 @@ actual object RealmInterop {
         return realm_wrapper.realm_user_get_identity(user.cptr()).safeKString("identity")
     }
 
-    actual fun realm_user_get_auth_provider(user: RealmUserPointer): AuthProvider {
-        return AuthProvider.of(realm_wrapper.realm_user_get_auth_provider(user.cptr()))
-    }
-
     actual fun realm_user_is_logged_in(user: RealmUserPointer): Boolean {
         return realm_wrapper.realm_user_is_logged_in(user.cptr())
     }
diff --git a/packages/external/core b/packages/external/core
index c258e2681b..f8604b9fd3 160000
--- a/packages/external/core
+++ b/packages/external/core
@@ -1 +1 @@
-Subproject commit c258e2681bca5fb33bbd23c112493817b43bfa86
+Subproject commit f8604b9fd3d2982008a1d3f5ff35e52ee9098d5b
diff --git a/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/User.kt b/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/User.kt
index fa4d7e3742..1fc0d1cb32 100644
--- a/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/User.kt
+++ b/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/User.kt
@@ -83,6 +83,7 @@ public interface User {
      * Returns the provider type used to log the user in.
      * If a user logs out, the authentication provider last used to log the user in will still be returned.
      */
+    @Deprecated("Property not stable, users might have multiple providers.", ReplaceWith("identities"))
     public val provider: AuthenticationProvider
 
     /**
diff --git a/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/internal/UserImpl.kt b/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/internal/UserImpl.kt
index c10d3a4971..ec96b5d864 100644
--- a/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/internal/UserImpl.kt
+++ b/packages/library-sync/src/commonMain/kotlin/io/realm/kotlin/mongodb/internal/UserImpl.kt
@@ -49,7 +49,7 @@ public class UserImpl(
     override val loggedIn: Boolean
         get() = RealmInterop.realm_user_is_logged_in(nativePointer)
     override val provider: AuthenticationProvider
-        get() = AuthenticationProviderImpl.fromId(RealmInterop.realm_user_get_auth_provider(nativePointer))
+        get() = identities.first().provider
     override val accessToken: String
         get() = RealmInterop.realm_user_get_access_token(nativePointer)
     override val refreshToken: String