Answer

A company Shareholder Rights Plan (also known as a “Poison Pill”) is a corporate defense mechanism used to prevent a hostile takeover of a public company. The target corporation uses a Poison Pill in order to make its stock less attractive.  Not all companies have a Poison Pill in place.  Generally, the Poison Pill has an expiration date and may be amended, extended or retired. A company will file its Shareholder Rights Plan with the company's SEC filings, generally as exhibit 4.1 to a Form 8-A or an 8-K. The plan can be tricky to find in the SEC filings.

Go to the NYU Business Library's Company & Financial Information section for links to useful resources including the following suggested resource: 

LSEG Workspace: Provides public company Poison Pill information.  Scroll over Search Tools on the toolbar and select Search.  In the search bar type in Corporate Governance.  In the results select Takeover Defenses or Latest Poison Pill. 

VitalLaw: Provides explanations about Poison Pills as well as white papers, laws, regulations, and case law.