用这个插件把某个网站的音量放大到 500% 挺好用的。

Security warning first: this copy of Volume & Sound Booster contains malware
Do not install this XPI. If it's installed in any of your browsers, remove it.

The real volume feature is the ~150 lines in cs.js. The other files (csvolume*.js, amplify-relay-bg.js) are pieces of unrelated libraries (Dark Reader, AdGuard scriptlets, lodash, Vue) with renamed functions. That filler hides a remote-control loader:

Delayed start: amplify-relay-bg.js:770-790 saves an install timestamp and does nothing for about 3 days (laneGapMs = 258200000). This is a common way to get past store review.
Hidden server address: csvolumepatch.js:808-812 calls cloudflare.com/cdn-cgi/trace to get a value h. That value is part of the key that decrypts the server URL, so the URL can't be read from the code alone.
Network rules from the server: amplify-relay-bg.js:825-840 downloads a payload and applies it with declarativeNetRequest.updateDynamicRules. That lets the server redirect requests or rewrite headers on any site.
Remote code in every page: csvolumepatch.js:850-890 runs code from that payload inside each page, using new Function(body)() or a function exported into the page via wrappedJSObject. It skips pages that contain a certain "guard" string.

Worked pretty well on youtube.