August 2015 CU Error – “File names can’t contain the following characters”

Update October 2015: This issue is resolved in security update KB3085582, SharePoint Foundation, SharePoint Server, and Project Server 2013 Cumulative Updates. Update to one of these patches rather than using the below method.

As noticed on a TechNet forum post, the August 2015 CU for SharePoint 2013 has a new regression with attaching files to List Items. This can be reproduced with a Custom List (possibly others) by creating a new List Item, clicking “Attach File”, identify any file that contains characters not listed in KB905231, then click OK. The error message “File names can’t contain the following characters” will appear:



A temporary workaround is available for this issue, but involves editing files in the 15 hive. Prior to performing this, make backup copies of these files. These backups must be in place prior to installing the next SharePoint patch.

There are two JavaScript files that must be edited:

C:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\TEMPLATE\LAYOUTS\FORM.debug.js

C:\Program Files\Common Files\microsoft shared\Web Server Extensions\15\TEMPLATE\LAYOUTS\FORM.JS

For Form.debug.js, change the text starting on line 5307 from:


And for FORM.js, find the following string:

Change it to:

Once completed, clear the browsers cache and re-test. If the error still exists, try using Inprivate browsing mode, which will not use the cache from the regular session.

A second workaround is also available, this does not involve any file editing.

In a List, create a List Item and save it without attempting to attach a file. On the List, highlight the specific List Item that was created. In the ribbon, click on Items -> Attach File. This dialog will allow you to successfully attach a file to a List Item.

A PSS case has been opened for this issue and the above solutions are the current official workarounds.


  1. Thanks! Very helpful, hope Microsoft will fix that in the next CU! I prefer the second workaround. Thanks.

  2. Pingback: SharePoint 2013 August 2015 CU contains a bug, some fix and a cool new feature | SharePoint Flying Pig's Blog

  3. thanks for sharing this, very useful.

  4. I tried your second workaround. Unfortunately it didn’t work for Calendar Events.

    • Thanks for letting me know. I will try to reproduce with a Calendar list.

    • This is something that worked for me. Once the calendar even has been created, click on the event to open it. Click on the Edit Item icon then Attach File. Browse to the file. Instead of clicking OK, click on Save at the upper left. Doing this allowed me to attach a file to the calendar event.

  5. I have confirmed that MS15-099 also generated this error. This is from test our environments with our without MS15-099.

  6. Thank you! I do need to make the JavaScript changes for my end users. Now I’ll need to watch for any affects the MS “fix” may cause after they implement it. Please update here if/when you here of MS releasing a fix for this.

  7. Thank you.
    We haven’t applied the work around yet as we also have another issue after August CU was applied….

    Results are correct if you navigate to a list and search within the list where:
    – Lists were created PRE Aug CU that have do not have attachments

    No Search if you navigate to a list and search within the list where:
    – Lists were created PRE Aug CU that have attachments

    No Search results shown if you navigate to any list created POST August CU where
    – the Lists has attachments.
    – the list doesn’t have attachments

    Has anyone else found this issue and is it a known bug yet?

    Apologies if this is in the wrong place.

  8. Muhammad Sami Ahmed

    I have applied September CU and the bug is still right there!!! :)
    For now I have adapted first workaround as it was production impacting.

    Thanks for you proposed workaround, I will research more on it.

  9. Awesome, thanks for the fix! It worked great for fixing the issue I was having with calendar entry attachments.

  10. Is the above 15 hive workaround supposed to be done on the server or the client workstation?

  11. Thank you very much for this post! The JavaScript fixes have solved the issue. We’ve just ran into this situation with SharePoint Foundation 2013. I suspect that the issue was caused by the patch KB3085501 on the grounds that as it says in Technet, it updates these two files. The patch was installed by the Windows Update, and users started seeing the issue. Prior to hacking the scripts I tried to run the psconfig, which successfully upgraded the farm to 15.0.4753.1000, but the issue didn’t go away, so your method has worked perfectly.

  12. Well, I made the changes on the server side for the FORMdebug and FORM js files. I still get the error with Internet Explorer 11.09…., However, It seems to work fine with Chrome.

    I had cleared my cache, tried inprivatebrowsing, but I keep getting the same error when I use Internet Explorer.

    Any ideas?

  13. This did not work for me. Perhaps Im just doing it wrong. I edited both of the .js files and it did not seem to do anything. Is it as simple as editing the file and just saving it in the same locations?

  14. Thanks Trevor. Do you know around what time the new updates will be released?

  15. As of the November 2015 CU for SharePoint 2013 this still does not seem to be resolved by Microsoft. As is being asked by others, is there any time table from Microsoft on this being fixed? Thanks.

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