In T151770#2890521, @matej_suchanek wrote:

Nothing but clearing (in tears) all my cookies helped. Everything was in order till yesterday when, all of sudden, it came back.

I'll put all my addons and Wikipedia gadgets here so that people can see whether there is any correlation, although I'll be checking through them myself later once I find a reliable way to set cookies to trigger the issue again. If it seems like too much effort, nobody needs to do anything with this list, but just in case someone spots something known or obvious...

Thanks for interpreting that, @Anomie. I tried reproducing the problem using scripts like this one and httpbin, but in each case it was possible to save more than 16 cookies. So if it is something in my browser, it is not affecting every site. I will investigate more later, to see whether some browser extension or Wikipedia gadget may be the cause, as I do have a few of each enabled.

In T151770#2874646, @Anomie wrote:

In T151770#2873767, @Legoktm wrote:

If browsers are corrupting cookies this often, we should work around it somehow and/or file upstream bugs.

I note no one who has been able to reproduce this bug has reported actually capturing the HTTP requests and responses or otherwise investigating the issue.

Seems to be behaving correctly for me now. Should probably wait a bit more before closing?

For me, the first one linked above in zhuyifei's comment looks like this:

It seems this image is also affected: https://commons.wikimedia.org/wiki/File:Glasl's_Model_of_Conflict_Escalation.svg