WebKitGTK through 2.26.4 and WPE WebKit through 2.26.4 (which are the versions right before 2.28.0) contains a memory corruption issue (use-after-free) that may lead to arbitrary code execution. This issue has been fixed in 2.28.0 with improved memory handling.
https://www.debian.org/security/2020/dsa-4641
https://wpewebkit.org/security/WSA-2020-0003.html
https://webkitgtk.org/security/WSA-2020-0003.html
https://usn.ubuntu.com/4310-1/
https://security.gentoo.org/glsa/202006-08
https://bugs.webkit.org/show_bug.cgi?id=204342#c21
http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00008.html