Recently Apple developers have released security updates, fixing three 0-day bugs in their porducts at once. Apple says, all of these problems could already have been exploited by hackers, which is obvious as the 0day Vulnerabilities before becoming public are exploited in the black market. 

All bugs affect the Webkit browser engine at the heart of the Browser Sadari. WebKit works in most of the company's products as a built-in component (including iPadOS, tvOS, and watchOS) that is used to display web content when there is no need to load a full browser.

They have provided fixes with with macOS Big Sur 11.3.1 ,   iOS 12.5.3 ,   iOS 14.5.1, iPadOS 14.5.1,  and   watchOS 7.4.1 , and the above 0-day vulnerabilities were assigned CVE-2021-30663, CVE- 2021-30665 and CVE-2021-30666. It is also worth noting that iOS 12.5.3 includes an additional patch for the CVE-2021-30661 bug. This is considered to be a new bug that was fixed a week earlier. 

Apple does not disclose the details of the vulnerabilities, as well as the information on the possible attacks done using those bugs.