The scandal poses a setback for Park, who already faces criticism that her leadership is similar to the heavy-handed style of her late dictator father, President Park Chung-hee.
Critics say the current president's poor communication with the public and lack of transparency on the personnel decisions she makes are to blame for the scandal.
The scandal centers on ex-aide Chung Yoon Hoe, who, according to local media reports, allegedly met regularly with 10 of Park's associates at a Seoul restaurant to try to exert influence on her personnel management.
Those reports are based on leaked presidential documents from an office headed by a presidential aide who's reportedly close to Park's brother, Park Ji-man. The Blue House says the documents contain groundless rumours.
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Today, prosecutors hauled in Park Ji-man for questioning, the latest in a slew of high-profile figures who have been summoned since a local newspaper first reported the speculation late last month.
Chung was summoned on Wednesday. On Saturday, one of three police officers being investigated over their roles in the document leaks was found dead in an apparent suicide.