Users who believe they could be affected should keep a close eye on their credit card statements and report any unknown charges. The use of the free credit monitoring provided by Warner should be taken advantage of as well. Operators of e-commerce sites need to carefully monitor activity on the webserver that hosts the checkout page, in order to take quick action if an unauthorized change is made to HTML or JavaScript. All such changes should be carefully reviewed to determine if they represent a threat. This requires careful attention to detail, because threat actors have hidden malicious JavaScript code in unlikely places, including the metadata of icon image files. Another method of protection when dealing with these attacks is a service such as Binary Defense’s typo-squatting monitoring, which involves searching for any registered domains that are similar to a company’s legitimate domain names and could be used for malicious purposes. In some previous cases, attackers have set up a fake version of a website on a look-alike domain name to trick customers into entering their password or personal information on the attackers’ site.
Source: https://www.zdnet.com/article/warner-music-discloses-months-long-web-skimming-incident/