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This issue affects systems where KTelnetService and a vulnerable version of Konsole are installed but at least one of the programs telnet, rlogin or ssh is not installed. The vulnerability is in KDE's terminal emulator Konsole. As stated in the advisory by KDE, Konsole versions < 25.04.2 are vulnerable.
On vulnerable systems remote code execution from a visited website is possible if the user allows loading of certain URL schemes (telnet://, rlogin:// or ssh://) in their web browser. Depending on the web browser and configuration this, e.g., means accepting a prompt in the browser.