I've had a really annoying problem where various sites weren't rendering properly. In many cases you could see garbled mess instead of text, if I remember correctly. I eventually figured out that it was Avast side-loading an extension, without explicit consent I might add, that was causing this.

Most AV software patch dlls, or inject their own code into running browsers.

Most AV software is basically malware itself.

They also work at the OS level or in kernelmode.

I thought they disabled these kinds of silently sideloaded extensions like five years ago. Or was that chromium only?

Yeah, they're disabled by default. But now they weren't install at all.

Anti viruses are typical bundleware installed when installing 'free' software. If you don't look carefully, when you click, 'i agree,' you'll get a bunch of other software you don't want.

Some crazy software companies then used a dark pattern - clicking 'I don't agree,' meant you agreed to install unwanted crap.

Adobe flash, Java runtime, utorrent and any installer from cnet.com are examples. That's why I installed Unchecky to protect me from bundleware and automatically uncheck, skip 'offerings' when installing new software.

Edit: As mentioned below, the Chrome team used bundleware extensively in its early days.

Chrome also did this at a massive scale. It's one of the many reasons why I will always prefer firefox.

Sometimes your organisation installs Mcafee, you then proceed to install Firefox.

In addition to this, many products come preinstalled as bloatware. McAfee products (amongst a hoard of other programs) have come preinstalled on Windows laptops I've purchased from Dell and Lenovo.

The "Fresh Start" feature in newer builds of Windows 10 (1709-onwards if I'm not mistaken) will automatically remove these kinds of applications preinstalled on new systems.

https://www.microsoft.com/en-us/software-download/windows10s...

Excellent feature. It's important to note that it's a good idea to have a copy of all of your devices' drivers before using it.

Excellent feature in itself, but also a cludge around a broken economic system. OEMs shouldn't be prioritizing their profits at the expense of the users their business exists for.

Then it's not your computer. What I meant is "the owner of the computer installs (or uninstalls) mcafee at will".