Avoid Using Incorrect MIME Types

MIME (Multipurpose Internet Mail Extensions) types are extensions that websites use to tell web browsers what kind of content the website is sending back to the visitor’s web browser. The web browser using the MIME type to determine how the website content should be processed. For example, a MIME type of text/plain would tell the web browser to treat the website data as plain text, while a MIME type of application/pdf tells the web browser to treat the website data as a PDF (Portable Document Format) file.

Web browsers will attempt to guess the MIME type of the website content if no MIME type is specified by the website; however, there is a chance that the web browser will guess the wrong type of content and not display the web page or website content correctly. Web browsers have actually moved away from attempting to guess MIME types because guessing MIME types can be a security hazard. It is possible for an attacker to craft a file with the wrong MIME type that web browsers would run instead of rejecting the file or confirming that the visitor intended to run that file.

WordPress websites generally set the correct MIME type for website content. However, issues with setting the correct MIME type may require changing the web server’s configuration to support additional MIME types or editing the website’s coding to set the correct MIME type for website responses. These kinds of changes should be made by experienced systems administrators or website developers.