These days mostly all the websites are ads supported. You can find promotional advertisement, on almost all website. It is hardly possible to know whether these ads are adding something fishy in your systems or not. For instance, if you find an ad on Wikipedia, then you should get extra cautious because Wikipedia is well known site for its ad-less approach to things.
Even the officials of Wikipedia are currently alerting the users about these ads. Recently Philippe Beaudette on behalf of Wikipedia stated in a review that if visitors see advertisements on the site, those ads have not been placed by Wikipedia and this is solely because the user’s systems have been infected with the malware. Thus in short, if you are viewing ads on Wikipedia, your system is malware infected.
According to a study, Google Chrome extension ‘I want this’ is found as one of the culprits for this job. If you see ads on Wikipedia and you are using Google chrome, then you should check if this extension is installed on your browser.
However the authorities do not claim with 100% surety that chrome is the only culprit for this job. May be other browser are also infected by the same malware. So to figure out whether it is your browser that is inviting malware to your system, run your browser without add-ons/extensions and check whether those ads are still present or not.
The authorized personnel also suggest checking the system with security software if advertisement is spotted on Wikipedia, or other locations on the Internet where it is usually not displayed. Also we suggest you to scan your system with Mbam (ultimate malware remover).
Be safe and be alert.