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Important Update: Movable Type 4.21 now available

By Byrne Reese
Posted August 21, 2008, in News.

In recent days two significant issues in the Movable Type 4.2 release were reported by our community. One of these bugs can potentially result in some form of limited data loss, and the other could cause loss of some configuration data in some circumstances. We have reproduced these issues as quickly as possible, and created patches to remedy the problems. Most users are not at any risk from these issues, but here are the circumstances under which you may have been affected:

  • Custom fields data. If you are upgrading from Movable Type Commercial or Enterprise 4.1 to Movable Type Pro or Enterprise 4.2 and you are using custom fields on any object in Movable Type and there are more than 100 rows in the table for that object, some of your custom field data could be lost in the migration.

  • Archive mappings. If you create a new blog on your Movable Type 4.2 installation and you delete an archive mapping from one of the archive templates, this action will remove the rest of your blog archive mappings inadvertently.

Both of these issues have been fixed and verified by our quality assurance team. The fixes can be found in the newly released Movable Type 4.21, a free update for all users of Movable Type 4.2. If you've downloaded 4.2, but have not yet upgraded, please download 4.21 first and then upgrade.

As always, please make a backup before performing any system update or upgrade.

To the best of our knowledge, only a very small number of people have been affected by this bug. To those people, we offer our sincerest apologies for any inconvenience or frustration. We work our hardest to prevent issues of this sort. It's thanks to our community that we've been able to find, fix, and respond to this issue so quickly. We appreciate your participation, and we thank you for using Movable Type.

  • If you're using a paid license of Movable Type Pro: Sign in to your account to download the update.
  • If you're using the free Blogger license of Movable Type Pro: Grab the code from
  • If you're using Movable Type: The open source download is right here.

As always, Enterprise customers and licensees will be personally contacted by a Six Apart account representative.


13 Comments on August 22, 2008, 5:48 a.m. Reply

An easy way to upgrade - but you must know what you’re doing :)

I was moving from 4.2rc5 and I found this very useful to my end, though it may be the wrong way for you! So, beware ;)

$ cd /path/to/your/mtos/installation/
$ cp -pR mtos mtos-bak
$ wget wget <a href=""></a>
$ rsync -a --progress MTOS-4.21-en/ mtos/

And that’s it. Just browse to your mt.cgi and get the MTOS automatically upgraded to MTOS 4.21.

Toni Hambilton

Toni Hambilton on August 22, 2008, 4:24 p.m. Reply

Thank you so much. This little tip turned my upgrade into a 3 minute process.


dolmance on August 25, 2008, 1:06 a.m. Reply

I upgraded from 4.1 to 4.2 before this patch and I lost all my custom fields data. That means I’ve lost a lot information hosted in more than 2000 posts. You should create a little script in order to help us to recover it. Thanks.


demonsurfer on August 26, 2008, 8:36 p.m. Reply

Hello. MT4.21com - the archive index has a whole bunch of {/mt:Ignore} tags misplaced, so entire archive listings are ignored.. the first few types of archives on that template are ok, such as

    <!-- List of category archives, if category archives are enabled -->

but then most of the remaining ones the {/mt:Ignore} tag is placed right at the end of the code for each archive listing type, rather than at the end of the message above.

Also I entered ticket 81593 on fogbugz for another issue. A new install fixed the problem, so if someone can please delete that ticket it would be appreciated.


demonsurfer on August 29, 2008, 7:12 p.m. Reply



JimAZtec on September 11, 2008, 1:41 p.m. Reply

I upgraded to from 4.12 everything went fine EXCEPT none of the comments appear. Even comment count does not show. What gives? on September 26, 2008, 11:49 a.m. Reply

I upgraded to 4.21 from 4.2, and now under “Refresh Blog Templates”, the “Apply a new template set” option is replaced by “Reset to factory defaults”. Is there a different way to apply a new template set?


Hank on September 11, 2012, 1:55 a.m. Reply

Hello, a question from curiosity here. If I lost my data in this or another way, am I able to restore it or it is gone forever?

Anne Sterten

Anne Sterten on October 26, 2012, 8:15 p.m. Reply

Hi, Dolmance. As far as I know in such cases you can not restore already lost information. This is why in Beta versions you need to make often back-ups of your data. If you haven’t you can check your hosting provider or as a final hope Google’s cache.


Evuns on November 15, 2012, 1:04 a.m. Reply

No need to sorry about anything. This is a beta version and this is what beta is made for - to fix bugs :)


james1989 on November 19, 2012, 8:25 a.m. Reply

Hi, is there a difference in the remedy between the paid and free users. Why the paid one should go into their account when the others could more easily (on the first sign) to grab the code from

Emma Howson

Emma Howson on December 14, 2012, 8:15 p.m. Reply

The remedy patch must be the same or there is no logic at all. So, don’t worry the Movable Type people are doing the same to all of their users without matter are they paid or not.

Amanda Jones

Amanda Jones on December 21, 2012, 6:54 a.m. Reply

This is a great service. To call directly to your costumers when you have a problem. Well Done MT :)

Byrne Reese

Byrne Reese was previously the Product Manager of Movable Type at Six Apart, where he had also held positions as the Manager of Platform Technology and Product Manager for TypePad. Byrne is a huge supporter of the Movable Type user and developer community. He dedicates much of his time to promoting and educating people about Movable Type as well as building the tools and plugins for Movable Type that are showcased on Majordojo. He contributes regularly to open source; and he is an advocate for open protocols and standards like Atom and OpenID.