PhpSpreadsheet is a PHP library for reading and writing spreadsheet files. The `XmlScanner` class has a scan method which should prevent XXE attacks. However, in a bypass of the previously reported `CVE-2024-47873`, the regexes from the `findCharSet` method, which is used for determining the current encoding can be bypassed by using a payload in the encoding UTF-7, and adding at end of the file a comment with the value `encoding="UTF-8"` with `"`, which is matched by the first regex, so that `encoding='UTF-7'` with single quotes `'` in the XML header is not matched by the second regex. An attacker can bypass the sanitizer and achieve an XML external entity attack. Versions 1.9.4, 2.1.3, 2.3.2, and 3.4.0 fix the issue.

PhpSpreadsheet is a PHP library for reading and writing spreadsheet files. The XmlScanner class has a scan method which should prevent XXE attacks. However, prior to versions 1.9.4, 2.1.3, 2.3.2, and 3.4.0, the regexes used in the `scan` method and the findCharSet method can be bypassed by using UCS-4 and encoding guessing. An attacker can bypass the sanitizer and achieve an XML external entity attack. Versions 1.9.4, 2.1.3, 2.3.2, and 3.4.0 fix the issue.