Plagiarism already been discussed in meta before:
The copy-paste issue, Hinduism version
To understand it more clearly Stack exchange main meta also have similar post
What to do when plagiarism is discovered
I am writing it word to word here for clearing it:
Important: Don't be a lynch mob, even if you're (understandably) angry. Do not pile downvotes on recently uncovered plagiators'
answers. Let the moderators handle it - they will destroy any
occurrences of egregious plagiarism, and may suspend the user for a
Check again whether the OP didn't add a source somewhere after all.
Sometimes it is at the end of the copied text, or hidden behind a
single-word link. Check out all the links in the answer. Sometimes
they get hidden by bad formatting - it's worth clicking 'edit' just
for one final check to make sure.
Make sure that the original source you found really is a legit
source, and not one of the ripoff sites copying Stack Overflow
content (efreedom.us, etc.) or some other content aggregator.
2. Edit or flag If it looks like a minor, single incident, editing the attribution in is the way to go. You can do that yourself,
either directly or through a suggested edit. Put the attribution in
front of the copied material, and put everything into blockquotes
that isn't the OP's original speech. Use nice wording, like
Wikipedia Article on xyz: After that, proceed to step 3.
If it looks like there is an egregious pattern of plagiarism,
and deletions seem necessary, flag for moderator attention. Explain
that you believe the answer has been plagiarized, and paste the source
URL into a comment underneath, say
Plagiarism: copied without
attribution from ....
If your flag gets declined, flag again and/or raise the issue on Meta.
Here is previous discussion.
3. Educate the OP The OP may be innocent(-ish) simply because they're ignorant of how gravely wrong plagiarism is - this is the
case more often than one would believe. If there is no indication the
community has had a conversation with them about the issue, consider
leaving a polite comment along the lines of
Hi, it appears that you copied this answer from (insert URL here). You're using someone else's work without giving the author credit.
This amounts to plagiarism, and is not welcome on Stack Overflow.
Remember to always add prominent attribution when using other
or a more nicely worded suggestion from JMort:
Hi User, it looks like you just copied most of this content from this blog . Can you edit your post and give attribution to the author?
Plagiarism isn't really welcomed on Stack Overflow, and it's always
nice to give credit where credit is due. Good luck!
4. Go hunt for more
Moderators have enough to do already - they won't be able to check out
a user's entire profile for further instances of plagiarism. If you
feel like it, take that task upon yourself, and flag each occurrence
as described above.
For "Opinion based answer”
We can refer Shog9's words as official statement to our different meta question :
We definitely don't want folks composing their answers entirely of
someone else's work, but backing up their assertions should
be considered normal.
These two ideals don't really conflict with each other either. You
should be able to summarize a scripture and relate it to the
asker's question in your own words, while still tying it back to a
more canonical source.
In other words, answerers should strive to share their own
interpretations but back them up by references to verifiable sources.