Webkit vulnerabilities in PS4 and PS5 refer to bugs found in the Webkit engine used by their web browsers. These bugs, discovered in browsers like Safari and Chrome, can also exist in PS4 and PS5 because they share the same Webkit codebase.  While a Webkit bug alone isn’t enough for a jailbreak, it can be a crucial first step, and exploiting such a vulnerability along with a kernel exploit (giving more system access) can potentially lead to a PS4/PS5 jailbreak.  The PPPwn exploit alone is not sufficient for a PS5 jailbreak due to the console’s strong security mitigations.

Source: GBHackers