Following login, users may see a 403 error due to CSRF verification

[StevenMaude]

…frequently when I login to OpenCodelists I get the following error. It does log me in, but I have to navigate back to the homepage.

https://bennettoxford.slack.com/archives/C01D7H9LYKB/p1709739999212329

The error is a 403 CSRF verification failed. Request aborted.

[tomodwyer]

I am not able to replicate the issue locally or on production.

[lucyb]

I also had a look, but it wasn't obvious why this might be happening. I believe it's happening on the redirect post-login rather than the login form, although it will require a bit more digging. If this is only affecting one user occasionally, I suggest that we leave it for now unless we get any more reports.