Click on the current bug severity to view and select the desired bug severity from the dropdown. Upon creation, the default severity of the bug is S1. The severity ranges from S1 (high) through S4 (low).
Users with view and edit permissions in bugs can perform this action. Depending on the settings of the user's project permissions, they may be able to view all the project bugs or just a subset of them. Watchers specifically added to the bug will be able to view it.