Apple's latest security updates address issues in the WebKit and WebKit Storage frameworks that allow maliciously crafted content to execute arbitrary code.
These vulnerabilities are reportedly being actively exploited.
The updates address CVEs 2021-30661, 2021-30663, 2021-30665, 2021-30666.
Three of the issues were discovered by members of the Qihoo 360 ATA team, and the fourth by an anonymous researcher.
There is no indication at this time whether older versions of macOS such as Catalina and Mojave are affected, or if any of the vulnerabilities are present and exploitable in tvOS.
"Apple users should update to the latest version of iOS, iPadOS, watchOS, and macOS on a regular basis to address vulnerabilities like these," said Tenable staff research engineer Satnam Narang.
"While it is often unlikely that these zero-days will be exploiteden masse, we still caution all Apple users to upgrade as soon as possible."