It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted URL-like text into the editor, and then press Enter or Space (in the Autolink plugin).
https://github.com/ckeditor/ckeditor4/blob/major/CHANGES.md#ckeditor-416
https://www.oracle.com//security-alerts/cpujul2021.html
Source: MITRE
Published: 2021-01-26
Updated: 2022-03-01
Type: CWE-829
Base Score: 4.3
Vector: AV:N/AC:M/Au:N/C:N/I:N/A:P
Impact Score: 2.9
Exploitability Score: 8.6
Severity: MEDIUM
Base Score: 6.5
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
Impact Score: 3.6
Exploitability Score: 2.8
Severity: MEDIUM