In general, the person who took the picture, or, in the case of an article, its author, is the copyright owner. Hence, if you took the picture or wrote the article yourself, you own the copyright. If someone else took the picture or wrote the article, the fact that you uploaded the picture or article does not make you the copyright owner. In fact, you would need the copyright owner's permission before uploading the picture or article.
Citizen journalist websites have their own policies or terms of use regarding copyright issues and this may vary from site to site. You should read these policies or terms of use before using the sites.
Often, citizen journalist websites expressly require you not to be in breach of copyright law when you upload material. Thus, you should be careful to upload only copyright material that you own, or for which clearance has been given, or where an exception applies. Through their stated copyright policy or terms and conditions of use, citizen journalist websites also typically obtain your license to reproduce and distribute the material you uploaded without the need to check with you each time they do so.
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