Wikipedia says it has blocked more than 300 accounts being used by people who are paid to create or tweak entries at the communally sourced online encyclopedia.
Weeks of investigation revealed 381 accounts were being used at the English version of Wikipedia for "black hat" editing in which people take money to promote outside interests without disclosing they are on someone's payroll.
Wikipedia is powered mostly by volunteers and bars paid advocacy that is not disclosed, such as in the case of museums or universities having employees tune entries related to exhibits or institutions.
"Neutrality is key to ensuring Wikipedia's quality," Ed Erhart and Juliet Barbara of the nonprofit Wikimedia Foundation said in the blog post on Wednesday.
"Although it does not happen often, undisclosed paid advocacy editing may represent a serious conflict of interest and could compromise the quality of content on Wikipedia."
Along with blocking the 381 "sockpuppet" accounts, Wikipedia editors deleted 210 articles created by people using those accounts. There was a potential for more entries to be removed as the investigation continued.
"Most of these articles, which were related to businesses, business people, or artists, were generally promotional in nature, and often included biased or skewed information, unattributed material, and potential copyright violations," Erhart and Barbara said.
"The edits made by the sockpuppets are similar enough that the community believes they were perpetrated by one coordinated group."
The accounts identified in during the investigation were used from the end of April to early August, but the nature and quality of edits suggested that the paid-scheme was operating "for some time" before being discovered, according to Wikipedia.
A team of volunteers tends to Wikipedia entries, which rely on crowd-sourcing for accuracy.
"Editing Wikipedia is completely free, and only requires compliance with the project's editorial guidelines," Erhart and Barbara said.
"No one should ever have to pay to create or maintain a Wikipedia article."