First, run a site backup -- both the database and static files on the server (e.g., theme files, image uploads). Ideally you'll also know or figure out how to restore the site with said backup. The plugin UpdraftPlus has a free tier you might start with. I use it on a personal site to run daily backups automatically, and have used it on employer websites in the past. You should be running daily backups if you... Source: 11 months ago

There is "Signed Pages" by the debeloper of EteSync. It is a browser extension, that checks webapps based on signatures in the html file. The addon then warns the user if the signature is not correct or - if I remember correctly - the source changed. This allows you to be sure what webapp code was delivered. But it seems like it did not really get used outside of his own projects. - Source: Hacker News / 4 months ago

EteSync has implemented something called Signed Pages, this might be worth looking closer at. This uses PGP keys which is preloaded into the browser; but I suspect that will be a barrier too high for most non-tech users. Source: about 1 year ago

There are also projects like signed web pages which can also help increasing the trust level to some degree. But that requires that you can download the source code and regenerate the verification hash locally - or have other trusted methods to verify the hash value hasn't been modified as well. The current concept is reasonably sane, but it requires too much from users currently to make it widely used. Source: almost 2 years ago

> The server can at any time start serving malicious payloads True, and I call this threat model "Beware Each and Every Fetch" (BEEF) in contrast to the more common TOFU model (although if you trust a desktop app to auto-update itself then these two models might not be all that different). In any case, I think you're being a little quick to dismiss the idea of server-hosted applications. It's true that browsers... - Source: Hacker News / about 2 years ago

Something like a browser extension for this does already exist, fortunately: https://github.com/tasn/webext-signed-pages. - Source: Hacker News / over 2 years ago