Google is taking security for Gmail to a new level. They recently updated the up with the capability to block third party add-ons that have the capability of snooping in your emails. They did this by implementing something called Content Security Policy, which stops web extensions from running code that has the potential to bypass security.
It's possible that some useful third-party add-ons will be disabled by this upgrade, but either they are legit and will get an update which restores limited functionality, or they were probably something you don't want to begin with. Here's the full quote below from Google's developer blog:
Posted by Danesh Irani, Software Engineer, Gmail Security
We know that the safety and reliability of your Gmail is super important to you, which is why we’re always working on security improvements like serving images through secure proxy servers, and requiring HTTPS. Today, Gmail on the desktop is becoming more secure with support for Content Security Policy (CSP).
There are many great extensions for Gmail. Unfortunately, there are also some extensions that behave badly, loading code which interferes with your Gmail session, or malware which compromises your email’s security. Gmail’s CSP protects you, by stopping these extensions from loading unsafe code.
Most popular (and well-behaved) extensions have already been updated to work with the CSP standard, but if you happen to have any trouble with an extension, try installing its latest version from your browser’s web store (for example, the Chrome Web Store for Chrome users).
CSP is just another example of how Gmail can help make your email experience safer. For advice and tools that help keep you safe across the web, you can always visit the Google Security Center.
Sound off and let us know if you use any third party add-ons for your Gmail.
Source: Official Gmail Blog