Starting with Firefox 79,
<area> elements having
target="_blank" will imply
rel="noopener" if no
rel attribute is set on the element, according to the current HTML spec. The
noopener link type makes
null in the new window, preventing the DOM property from being abused by untrusted third-party sites. If needed, explicitly setting
rel="opener" reverses the course.
Apple made the change first with Safari 12.1 shipped in March 2019. In Firefox, the new behaviour has been enabled by default in the Nightly and early Beta channels since Firefox 65. Google Chrome may also follow.
It’s a good idea to take this opportunity to check your code for
window.opener and understand what’s actually the