Issue with redirection back to item preview after login

[irbian]

After login, It redirects to es/component/users/?task=user.login&Itemid=101, where it shows a error 500 and a message like Additionally, a 500 Internal Server Error error was encountered while trying to use an ErrorDocument to handle the request.

Joomla 3.8.1 Flexicontent 3.2.1.7

[ggppdk]

You need to login first to frontend,

• and then click on the preview link at the backend management

Does it work if you do the above ?

[irbian]

Really really strange

At first, this message happened on two different installations with the same versions

After your comment, I tried again to reproduce, but now it works! The preview button on the item form works as expected (it goes to the login page, and later, to the article)

What I can see is that the preview button on the item list don´t redirect me to the login page, the same way the one in item form works

Anyway, if I reproduce the problem again, I´ll let you know

[ggppdk]

Question did you make 1 unsuccessful login ? (maybe issue happens after 1 unsuccesful login)

i mean you tried to login and password was wrong and you the login form reloaded

and then on 2nd or 3rd try you were succesful to login ?

If it is like above, then it sound look a bug in Joomla users component

[irbian]

I tried to reproduce it again with my client

The preview button tries to go to "'/site/27-category/174-articletitle?preview=1'"

This redirect to "es/?option=com_users&view=login&return=longalfanumericstring&fcreturn=anotherlongalfanumericstring"

When I try to identify (with the correct credentials), this redirect me to "es/component/users/?task=user.login&Itemid=103" where I can see this error

`Internal Server Error

The server encountered an internal error or misconfiguration and was unable to complete your request.

Please contact the server administrator at postmaster@mydomain.com to inform them of the time this error occurred, and the actions you performed just before this error.

More information about this error may be available in the server error log.

Additionally, a 303 See Other error was encountered while trying to use an ErrorDocument to handle the request.`

If I log in previously on frontend, and push preview, there is no problem

[irbian]

Actually, I have seen something strange on the longalfanumericstrings. They are base64encoded parameters, but it looks like they are not properly encoded? I decoded my parameters and they show something like this for the first one:

"http://mydomain.com/es/site/27-category/174-articletitle]Y]L"

That strange characters at the end of the url...

Actually, I got it! :D that's why its random

I encoded the url where it has to go, and the encoded string is almost the same as the one flexicontent build... except for one character

The one from flexicontent: aHR0cDovL3d3dy5nYWJyaWVsbGVrb25hbGkuY29tL2VzL3NpdGUvMjctZXZlbnRvcy8xNzQtZWwtbHVnYXItcGVyZmVjdG8tcGFyYS1lbC1zaS1xdWllcm8_cHJldmlldz0x

The one when I encoded: aHR0cDovL3d3dy5nYWJyaWVsbGVrb25hbGkuY29tL2VzL3NpdGUvMjctZXZlbnRvcy8xNzQtZWwtbHVnYXItcGVyZmVjdG8tcGFyYS1lbC1zaS1xdWllcm8/cHJldmlldz0x

Did you spot the difference? it changes the / with _. I guess that is some kind of cleaning measure for the url params, but without looking at the code I don´t know if the problem is in your side or in the Joomla side

That´s why this problem is not as easy to reproduce, because it depends if the base64decoded contains a slash

[ggppdk]

1 of the reasons that we have fcreturn

• is that the the encoding that joomla login form does is bogus it does not encode some characters correctly (i do not remember all details now, i just remember encoutering this )

we propably need to overwrite value of &return= with the value of &fcreturn using the onAfterInitialize system event

[iamrobert]

I am also having this Internal Server Error issue with the following error message:

[Fri Apr 13 18:27:26.754961 2018] [http:error] [pid 1224:tid 1860] [client ::1:57477] AH02430: Response header 'Location' value of 'http://localhost/iis7/114-news/741-demo-article\x1b\x18[\x99\xcfY[\x89\x9c\x1c\x99]\x9aY]\xcfL' contains invalid characters, aborting request, referer: http://localhost/iis7/index.php?option=com_users&view=login&return=cccc,&fcreturn=xxxx