Steps to reproduce the issue

When entering the following string into an article and trying to save. An exception is thrown.

"mailto:dummy@dummydomain.com\"

This is seemingly caused by the backslash before the quote.

This can happen if you have markup stored in json:

{"content":"<p>Email: <a href=\\"mailto:dummy@dummydomain.com\\">dummy@dummydomain.com<\\/a><\\/p>"}

Expected result

No error should be thrown.

Actual result

An exception with Prohibited input U+0000005C is thrown.

System information (as much as possible)

Joomla 6.0

Additional comments

In previous Joomla versions (e.g. 5.4.0) this did not happen.