Summary

When performed in a certain way (the replication steps is below), the menu where new issues are created uses the attachment from the previous created issue.

Steps to replicate

1. Create an issue in a new tab (separate from the dashboard)
2. In this new issue, include an attachment
3. In the newly created issue, try to create an issue in another new tab
4. Scroll down the page, and in the attachments section, the attachment from the previous created issue will already be attached

P.S.: If you disable the Issue Create pop-out as you can see here, the same behaviour will occur.

A screencast has been inserted for easier understanding and replication

Workaround

• If the new issue is not created in a new tab (for example, if it is created in a pop-up window that is generated by directly clicking on the 'Create Issue' button), the attachment would not be carried over

Other facts

• This was tested in JIRA 6.0, 6.0.4, and 6.0.8. Only JIRA 6.0.8 seems to be affected among the three