Preview not working for custom cultures

[craigFactory73]

Which Umbraco version are you using?

13.9.2

Bug summary

Hi All,

Recently page previews have stopped working on non standard cultures. We use the culture "en-JP" culture on a few sites which is not a default windows culture. This used to be fine but it looks like in an update to version 13.7 the following change was made:

343867f

To validate that the culture exists and avoid XSS attacks. The problem is that the the method:
ValidateProvidedCulture() calls
CultureInfo.GetCultureInfo(culture, true);
which is being passed 'true' for the 2nd parameter which indicates (from MS docs):

https://learn.microsoft.com/en-us/dotnet/api/system.globalization.cultureinfo.getcultureinfo?view=net-9.0

predefinedOnly Boolean
true if requesting to create an instance of a culture that is known by the platform. false if it is ok to retreive a made-up culture even if the platform does not carry data for it.

As our culture is 'made up' the call above does not retrieve it and the check fails, this results in a 500 error and a broken preview. Example preview link:

/umbraco/preview/?id=1000&culture=en-JP

InvalidOperationException: Could not recognise the provided culture: en-JP
Umbraco.Cms.Web.BackOffice.Controllers.PreviewController.Frame(int id, string culture)
lambda_method8051(Closure , object , object[] )
Microsoft.AspNetCore.Mvc.Infrastructure.ActionMethodExecutor+SyncActionResultExecutor.Execute(ActionContext actionContext, IActionResultTypeMapper mapper, ObjectMethodExecutor executor, object controller, object[] arguments)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeActionMethodAsync>g__Logged|12_1(ControllerActionInvoker invoker)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.<InvokeNextActionFilterAsync>g__Awaited|10_0(ControllerActionInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Rethrow(ActionExecutedContextSealed context)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ControllerActionInvoker.InvokeInnerFilterAsync()
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeNextResourceFilter>g__Awaited|25_0(ResourceInvoker invoker, Task lastTask, State next, Scope scope, object state, bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Rethrow(ResourceExecutedContextSealed context)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.Next(ref State next, ref Scope scope, ref object state, ref bool isCompleted)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.InvokeFilterPipelineAsync()
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)
Microsoft.AspNetCore.Mvc.Infrastructure.ResourceInvoker.<InvokeAsync>g__Logged|17_1(ResourceInvoker invoker)

I created the attached console app to confirm (renamed from .cs to .txt so I could attach) this and got the following results:

Program.txt

Running: CultureInfo.GetCultureInfo("en-JP", true)
Culture not found in list. Exception message Culture name 'en-JP' is not a predefined culture. (Parameter 'name')
en-JP is an invalid culture identifier.

Running: CultureInfo.GetCultureInfo("en-JP", false)
Culture exists in list with False parameter

Changing this flag to false would be just as secure and would allow previews even with custom cultures.

Specifics

Visit the url:

/umbraco/preview/?id=1556&culture=en-JP

While logged in and ensure the id exists to see the error. You don't need to actually have an en-JP culture setup.

Steps to reproduce

Create a node in the admin and preview it. Change the culture to en-JP in the query string.

Expected result / actual result

Error message from above.

---

This item has been added to our backlog AB#55099

[github-actions]

Hi there @craigFactory73!

Firstly, a big thank you for raising this issue. Every piece of feedback we receive helps us to make Umbraco better.

We really appreciate your patience while we wait for our team to have a look at this but we wanted to let you know that we see this and share with you the plan for what comes next.

• We'll assess whether this issue relates to something that has already been fixed in a later version of the release that it has been raised for.
• If it's a bug, is it related to a release that we are actively supporting or is it related to a release that's in the end-of-life or security-only phase?
• We'll replicate the issue to ensure that the problem is as described.
• We'll decide whether the behavior is an issue or if the behavior is intended.

We wish we could work with everyone directly and assess your issue immediately but we're in the fortunate position of having lots of contributions to work with and only a few humans who are able to do it. We are making progress though and in the meantime, we will keep you in the loop and let you know when we have any questions.

Thanks, from your friendly Umbraco GitHub bot 🤖 🙂

[nikolajlauridsen]

Fixed in #19821, thanks for reporting 👍