Making changes to the ongoing sprint as a scrum master

• Do you own the Sprint Backlog, or does the Development Team own it?
• As a Scrum Master, do you think a "release testing phase" is a timely way to identify bugs and triage them?

@Aishwarya Ravindra Bhosale, When you say "backlog" which backlog are you referring to? Sprint Backlog or Product Backlog?

If there are bugs, would you truly be able to achieve your Sprint Goal? Would the Increment meet the Definition of Done?

So can I put this all lower priority bugs in the backlog as a role of Scrum Master or development team?

Yes you, as a Scrum Master, can move things from one backlog to the other as long as the entire Scrum Team is asking you to do it and you are not making the decisions for them.  In this case it sounds like the appropriate conversations have occurred and a decision has been reached by the Scrum Team.  At this point I really don't see any reason the Scrum Master can't move items.  But if I were the Scrum Master I would be asking the rest of the Scrum Team who is going to update the respective backlogs. The Product Owner owns the Product Backlog, the Development Team owns the Sprint Backlog.  They are the ones that should decide what lives in each one. And moving an item is not a real time consuming activity so it seems that they could do it instead of expecting you to do it for them. 

Thanks for all quick response.It is really helpful@Daniel Wilhite. @ Ian Mitchell Currently , Development team owns the sprint backlog ; but as per my understanding anyone can change the sprint backlog as a part of team except PO. and I do think that release testing phase is only the way to identify and solve the bugs but it should not disturb the ongoing sprint. @Steve Matthew , I meant for sprint backlog, and for sprint goal , it is nothing to do with the fixing bugs only in case of lower priority because it does not achieve any sprint goal as we have different topics for sprint.The another question I have if we have release phase (approx for 2-3 months), is it necessary to have different sprint which is dedicated to "Release Testing Phase"? Does it make sense? so that it won't disturb any work for the ongoing sprint for the development team.

but as per my understanding anyone can change the sprint backlog as a part of team except PO

Anyone in the Development team yes... So, are you part of the Scrum tem or the Development team as SM?

and I do think that release testing phase is only the way to identify and solve the bugs

Does anyone have any thoughts on how this might be improved? Might you be creating a waterfall in te sprint this way?

it is nothing to do with the fixing bugs only in case of lower priority

I might be misuanderstanding, but are you saying you are fine with creating Technical Debt, even if these are no major findings? if so, does the Scrum Guide say anything about the quality of the Increment?

if we have release phase (approx for 2-3 months)

Do you think having a release phase after three months impacts empiricism? Does it impact the Inspect and Adapt cycles?

is it necessary to have different sprint which is dedicated to "Release Testing Phase"?

This fact you ask, might be a good indication towards the answer of my previous question... If are doubting if you need a release testing phase, might it not be a good indicator something can be improved there?