SSI-style HTML comments inside href attributes are broken when Source button is clicked

[Jordan Bradford]

SSI-style HTML comments such as <!--#echo var='DOCUMENT_NAME' --> become broken when the Source button is clicked.

Example:

Using the CKEditor demo site, click the Source button and add that comment to the first link:

<a href="http://en.wikipedia.org/wiki/Fairy_tale/<!--#echo var='DOCUMENT_NAME' -->" title="Fairy tale">fairy tale</a>

Then click Source to view the content in the normal editor mode. When you click Source again, the link becomes this:

<a href="http://en.wikipedia.org/wiki/Fairy_tale/{C}<!--#echo var='DOCUMENT_NAME' -->" title="Fairy tale">fairy tale</a>

Note the {C} that has been added. In fact, every time the source is viewed, another {C} is added:

<a href="http://en.wikipedia.org/wiki/Fairy_tale/{C}{C}<!--#echo var='DOCUMENT_NAME' -->" title="Fairy tale">fairy tale</a>

<a href="http://en.wikipedia.org/wiki/Fairy_tale/{C}{C}{C}<!--#echo var='DOCUMENT_NAME' -->" title="Fairy tale">fairy tale</a>

and so on.

[Jakub Ś]

DUP of #8216

[Piotrek Koszuliński]

I'm reopening this ticket, because it wasn't fixed together with #8216, so it might look as a duplicate, but it's a different case apparently.