PS : it happen with a copied survey : seems this settings is set 'Open' by default.
Unsure what happen when update

Just have a urgent call by a prospect about this issue.

By default.. INSERT a record ommitting access_mode will result in access_mode = 'O'

A closer look... access_mode seems obsolete. It is not used in the code anymore.

We had all sorts of issues with tokens in the most recent versions
We went back to 6.15.1+250625 and all is well again! It works like a charm!

I just test on https://shnoulle.limesurvey.net

If you leave Open access mode when activate :

Even with token table : you can enter survey
https://shnoulle.limesurvey.net/327729?newtest=Y
https://shnoulle.limesurvey.net/327729?token=TOKENTEST&newtest=Y

I noticed just now... in lime_survey table 'access_mode' ('O' default or 'C') is introduced in 6.15.7.
So it is brand new. But I think this setting is not very good implemented yet.

For us one thing is very clear... Token management is faulty in 6.15.7 and 1 or 2 versions before that.

token management:
6.15.4 is OK
6.15.5 onward Fails

correction 6.15.4 is also at fault...
6.15.3 is OK

As of 5.16.4 this form is not shown anymore (restore old tokens)
So for us 5.16.3 is the fixed version. Until tokenmanagement is completely fixed

Schermafbeelding 2025-08-25 112534.png (60,956 bytes)   

Schermafbeelding 2025-08-25 112534.png (60,956 bytes)   

correction...
As of 6.16.4 this form is not shown anymore (restore old tokens)
So for us 6.16.3 is the fixed version. Until tokenmanagement is completely fixed

see also https://bugs.limesurvey.org/view.php?id=20235

For what it is worth:
IMHO: https://github.com/LimeSurvey/LimeSurvey/pull/4300 is causing the issues

When

1. Activate and set "Closed access mode"
2. Deactivate
3. Activate : Closed access mode is not set by default.

I already activate 2 times a lot in less than 2 minutes.

Management of tokens is failing big time.
We are locked to version 6.15.3 and wait for better times.

We are locked to version 6.15.3 and wait for better times.

Reason why i create https://github.com/SondagesPro/LimeSurvey-SondagesPro/tree/temp/6.15.3_token with security fix

Sorry about the issue you are encountering. I will create a ticket for our internal team and we will work on it next sprint.

In the meantime there is a workaround, but it is far from optimal.
You can deactivate the survey in open access mode, reactivate it in closed access mode and restore participants and responses.

But when surey is lauched : you broke all access…

I think I have issue with some survey activated before 6.15.3 and was set as open mode after update …
I need to check this too.