Turkish Character "İ" or "ı" at Page Title Causes Links with Titles Unreachable

Hi,

After upgrading confluence to latest version(5.8.13) from 5.7.1, we got an issue with links which were created(before Confluence upgrade) with Page Titles. If a link has Page IDs(not contains Title of the page), problem is not observed. We have tested the other Turkish characters ('Ö', 'ö', 'ü', 'Ü') and problem not occurs with them.

Follows the given steps below to reproduce the issue:
1. Have a Page or create under any space with Title contains Turkish characters 'İ' or 'ı'.
2. Link this page with its title in another page. Or try to browse the link in any browser.
3. Link is not reachable. Page not found error occurs at Confluence.

For i.e.:
Space Code: SBP
Page Title: Yazılım Destek

Write the URL, which contains title instead the Page ID, in a browser and enter: https://<domain>/confluence/display/SBP/Yazılım+Destek
The above example fails to browse into the mentioned page.

But if you have a link without "İ" or "ı" the following works fine: https://<domain>/confluence/display/SBP/Uygulama+Destek

We have lots of links created previously at our system, so after upgrade we have trouble with this and it is not possible to change all of the links with their Page IDs as workaround.

Moreover some existing links, which contain 'İ' or 'ı' and works fine before upgrade, seem corrupted like as below:(so when a user click the link, confluence tries to create a new page):
https://dev.obss.com.tr/confluence/pages/createpage.action?spaceKey=OP&title=%C4%B0dari+B%C3%B6l%C3%BCmler&linkCreation=true&fromPageId=9864257

I should also say that we have lots of customers at Turkey as we are an Atlassian Platinum Partner, if they upgrade their confluence instances, they will also face with this issue too.

The issue has side effects to cause another problems. One of them can be reproduced like as below(blocker cannot create child pages):
1. Go to a page which contains "İ" or "i" (i.e.: İklim Sorunu)
2. Try to create a child page under the page mentioned at step 1.
3. Give any name to child page(even with English Characters.i.e.: Software)
4. Enter Save button to finish creation process.
5. Observe that the following Exception occurs at the page screen.

The following error(s) occurred:
The parent page specified does not exist. It may have been renamed or deleted since you started editing.

We think that this is one of the side effects caused by link issue.

I give some information at Environment Field about Server System and Confluence:

Please feel free to ask if you have more information.

Regards,
OBSS RCM Manager
Baki ÜNLÜ