Safe Exam Browser Unrecoverable Error with Moodle

[mmorak]

Describe the Bug
After logging into Moodle to access a quiz, the browser crashes. Log contains no relevant info, windows Event Viewer shows a NullReferenceException was thrown but not caught.

Steps to Reproduce
Steps to reproduce the behavior:
2. Click on "Start SEB" in a Moodle quiz
3. Log into Moodle again after SEB started
4. See error

Expected Behavior
Quiz should be shown.

Screenshots
If applicable, add screenshots to help explain your problem.

Version Information

• OS: Windows 10 22H2
• SEB-Version 3.10

Windows Event Log Entry
Log Name: Application
Source: .NET Runtime
Date: 10 Oct 2025 11:36:17
Event ID: 1026
Task Category: None
Level: Error
Keywords: Classic
User: N/A
Description:
Application: SafeExamBrowser.Client.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: System.NullReferenceException
at SafeExamBrowser.Browser.Integrations.MoodleIntegration.TrySearchByCookie(CefSharp.Cookie, System.String ByRef)
at SafeExamBrowser.Browser.Handlers.CookieVisitor.Visit(CefSharp.Cookie, Int32, Int32, Boolean ByRef)

[dbuechel]

We are not able to reproduce the issue. Please provide the entire log files (and line information of the stack trace, if available) and/or a test access to your system and/or a video which allow us to reproduce resp. review the issue in detail.

[mmorak]

Unfortunately, the Windows Event Log does not contain any more information than what I provided above.

I attach the log files here, but again, they are not very informative; this is the relevant bit from Runtime.log:

2025-10-10 11:36:17.574 [13] - INFO: [SessionResponsibility] ### ---------------------------------------- Session Running ----------------------------------------- ###
2025-10-10 11:36:22.779 [20] - ERROR: [ClientResponsibility] Client application has unexpectedly terminated with exit code -1073741819!
2025-10-10 11:36:22.779 [20] - INFO: [SessionResponsibility] ### ------------------------------------- Session Stop Procedure ------------------------------------- ###

2025-10-10_11h31m46s_Browser.log
2025-10-10_11h31m46s_Client.log
2025-10-10_11h31m46s_Runtime.log

Looking at the MoodleIntegration.TrySearchByCookie method in the repo, a NullReferenceException could occur when cookie or cookie.Name is null, for example. I don't have time to debug it myself, though :/

[dbuechel]

Thanks for the logs and sorry for the late reply. From what I know, a cookie passed from the visitor should never be null or not have a name, but I may err. Either way, we need to know on which line the exception exactly occurs in order to continue investigating it.

It's also a bit strange that the crash does not happen immediately after the initiation of the cookie traversal, but quite a while afterwards and seemingly while no particular browser activity is occurring.

Could you please export the entire event log entry from the Event Viewer application of the system and provide it here?

[dbuechel]

@mmorak If possible, could you please provide a minimal setup (Moodle quiz) which reproduces the crash? I fail to reproduce the issue with the setup provided under #1327 (as to why that is I'm still trying to figure out), hence it would be of great help if you could provide an additional way to reproduce the problem.

[mmorak]

I've just re-tried it with the latest SEB and it still produces the issue. I have attached the XML of the exported Windows Event Viewer.

Unfortunately, our university forbids access to our internal moodle instance without a university account, so I cannot provide such access. Here is some more info about the crash, however:

• starting the moodle quiz opens a new window, which remains blank until the crash (fullscreen popup with javascript security)
• SEB hangs for a short while immediately before the crash (mouse stuttering, CPU@100%)
• happens for any moodle quiz I create, not just one specific case
• we use a single sign-on system to log onto moodle

sebcrash.xml