Because of Internet Explorer 11

2022 was the year that Microsoft retired its Internet Explorer web browser (to concentrate on its Chromium-based Microsoft Edge browser).

Yet Ghacks reports that Internet Explorer "is still haunting some from its grave." Some websites and apps use code to determine the user agent. The user agent informs the site about several parameters, including the used web browser (engine) and operating system. When done correctly, it may reveal the used browser and that may then lead to a custom user experience.

When done wrong, it can lead to false identification on some websites. The inaccurate user agent sniffing is what causes some sites to identify Firefox as internet explorer.

Internet Explorer 11's user agent ends by identifying its release version as rv:11.0, the article points out. So when a Firefox user visits a website using Firefox 110 (or any other version up to Firefox 119), "The site in question checks for rv:11 in the user agent [and] Firefox's rv:110 value is identified wrongly as Internet Explorer."

Mozilla decided to freeze part of Firefox's version because they didn't want to risk problems withFunctionality, Compatibility, or other display issues rv:109 is returned instead of rv:110, rv:111 and so on up to rv:123. The end of the user agent string shows the current version of the browser. The original user agent of Firefox will be restored with the release of the new version. The organization plans to release a new version of the browser.