I've tried the solutions (changing system proxy to no proxy, clearing cache). Since updating from Version to 48 to Version 53.0.2 (yes, I skipped the versions in between), everything seems to work fine except for one website (the El Cohete Blog, http://5ftlatina.com/cohete/) which gives me the following error: QUOTE: Your access to this site has been limited Your access to this service has been temporarily limited. Please try again in a few minutes. (HTTP response code 503) Reason: Advanced blocking in effect. Important note for site admins: If you are the administrator of this website note that your access has been limited because you broke one of the Wordfence blocking rules. The reason your access was limited is: "Advanced blocking in effect.". If this is a false positive, meaning that your access to your own site has been limited incorrectly, then you will need to regain access to your site, go to the Wordfence "options" page, go to the section for Rate Limiting Rules and disable the rule that caused you to be blocked. For example, if you were blocked because it was detected that you are a fake Google crawler, then disable the rule that blocks fake google crawlers. Or if you were blocked because you were accessing your site too quickly, then increase the number of accesses allowed per minute. If you're still having trouble, then simply disable the Wordfence advanced blocking and you will still benefit from the other security features that Wordfence provides. If you are a site administrator and have been accidentally locked out, please enter your email in the box below and click "Send". If the email address you enter belongs to a known site administrator or someone set to receive Wordfence alerts, we will send you an email to help you regain access. Please read this FAQ entry if this does not work. END QUOTE I am NOT an owner of this web site, just a browser. I can access it with no problem in Chrome. I lost access via Firefox when I upgraded from Version 48 to 53.0.2 last week. (I have checked it daily. No change in the message.) Repeat: I can access all the other websites I visit regularly. I made NO changes to my system other than the upgrade to Firefox.