It is possible to apply bulk changes on issues. These changes may be made from multiple locations. 

From the Issues Service

Execute your search query and click on Bulk Change. You can then apply bulk changes to the issues returned by the search:

Since version 4.0, notifications are not sent for bulk changes by default. To explicitly send notifications, check Send notifications.

From the Component Viewer

Bulk change is available at the component level as well. Using the component-level dropdowns to narrow the selected list of issues, you can perform bulk changes such as: