There are some reports of users on en:WP:VP/T that they had no diff styling anymore. It was figured out that some users were getting: "Scripts should use an informative User-Agent string with contact information, or they may be IP-blocked without notice." on the below URL, even though they were using FF15 and Google Chrome.

http://bits.wikimedia.org/en.wikipedia.org/load.php?debug=false&lang=en&modules=mediawiki.action.history.diff&only=styles&skin=vector&*

I think that this might have been due to squid caching + client side caching of the URL?

Probably failures like that should aggressively make sure that they are not client side cached (Cache-Control: no-cache, must-revalidate instead of public), and have a short squid caching (a minute should be more than plenty to withstand any trouble right ?).

Version: wmf-deployment
Severity: normal