we're not running any modifications that would impact caching and we don't have any custom caching logic. we're only caching what lemmy/lemmy-ui return as cacheable, which suggests that the issue is likely in one of those services, however, i couldn't find it in either one.

it's also rare enough that it's extremely difficult to troubleshoot, as we see people report this maybe once or twice every few months but without any useful information that would allow us to look into this further than trying to find bugs in related code just from the general symptom of seemingly invalid cache.

additionally, the impact of this should be fairly low, as, unless this somehow impacts private messages as well, no data would be returned that isn't already otherwise public. with this seemingly "just" being a caching issue, there is also no risk at impersonating other users.

nonetheless i agree that this should not be happening in the first place, even if it's rare and the impact appears limited.

There's a reason recommendations nowadays are to use other instances than LW. Being the largest instance brings some unique situations.