iFrames are evil
I remember telling a copy & paste wannabe web designer in about 2003 that iFrames were evil. First introduced in MSIE in 1997?
I wondered were they invented to embed third party sites?
They seemed like a way to have your content "spoiled" by changes to the 3rd party site and also a risk to the user.
No responsible Webpage designer or site owner should be using them. Adverts can be done ethically without them.
Today I use uMatrix to block 3rd party scripts and only manually whitelist needed for functionality scripts. Even then I don't save changes unless a clearly safe 3rd party. These scripts are usually in iFrame elements. I used to use NoScript.