There was a bug in some versions of One-Click Postage that prevented adding tags that included the letters “J” and “K” (tumblr’s keys for jumping through the posts.) This has been fixed in version 2.9, and the page shouldn’t “jump” while typing tags.

You should get the new version in a few hours, but if you don’t want to wait, here’s how to update it manually (recommended):

1. Click on the X icon on your dashboard
2. Click on Manage Extensions
3. Select One-Click Postage 2
4. Click on Re-install / Manually Update this extension
5. Refresh the pages.

Sorry for any inconvenience, and thanks for using XKit!