Ad injection can cause other problems, too, especially when combined with people whose understanding of technology is lacking.
A few years back I got a job to do a wordpress site for a client. However, I wasn't dealing directly with the client, I signed on through a friend who was a fellow staff member of a forum I frequented. He agreed to create their site despite the fact that he was almost entirely technologically illiterate. His skills were at the 'barely read email' and 'be puzzled by OSX window decorations' sort of level. So, I agreed to do the job.
After working on the site for a couple of weeks, one day I received a call from him. He was quite upset as he was seeing porn ads and random nonsense characters on the blog. I investigated and found no trace of ads or foreign code, using several devices and several separate Internet connections. However he could see the ads on multiple devices in his house. Attempts to get him to try another Internet connection like his phone service were unsuccessful. I was pretty sure there was nothing wrong with the site, which was hosted on my VPS along with a couple of other sites that had no sign of issues. However he grew progressively more worried that the client would see these ads on the page, which was live for some reason. I even engaged the help of 20 or so people from the forum to check and they all agreed that no porn ads were visible to them. However this just upset my friend more as he felt embarrassed, but still convinced there was a problem. I suspected he had a virus on the systems at his house (all Apple...) or his router. It ended up with me being banned from his forum and being forced to quit the job... Before finally someone reset his router and the porn ads disappeared.
So, content appearing from unknown sources has definitely caused me problems in the past.
A few years back I got a job to do a wordpress site for a client. However, I wasn't dealing directly with the client, I signed on through a friend who was a fellow staff member of a forum I frequented. He agreed to create their site despite the fact that he was almost entirely technologically illiterate. His skills were at the 'barely read email' and 'be puzzled by OSX window decorations' sort of level. So, I agreed to do the job.
After working on the site for a couple of weeks, one day I received a call from him. He was quite upset as he was seeing porn ads and random nonsense characters on the blog. I investigated and found no trace of ads or foreign code, using several devices and several separate Internet connections. However he could see the ads on multiple devices in his house. Attempts to get him to try another Internet connection like his phone service were unsuccessful. I was pretty sure there was nothing wrong with the site, which was hosted on my VPS along with a couple of other sites that had no sign of issues. However he grew progressively more worried that the client would see these ads on the page, which was live for some reason. I even engaged the help of 20 or so people from the forum to check and they all agreed that no porn ads were visible to them. However this just upset my friend more as he felt embarrassed, but still convinced there was a problem. I suspected he had a virus on the systems at his house (all Apple...) or his router. It ended up with me being banned from his forum and being forced to quit the job... Before finally someone reset his router and the porn ads disappeared.
So, content appearing from unknown sources has definitely caused me problems in the past.