[2] Harrison accompanied National Security Agency whistleblower Edward Snowden on a high-profile flight from Hong Kong to Moscow while he was sought by the United States government.

[7] As an intern at the UK-based Centre for Investigative Journalism, Harrison began working with WikiLeaks in August 2010 and was assigned to Julian Assange before the Afghan War documents leak.

[2][11][6] In 2014, Harrison spoke about her support for WikiLeaks, saying "the greatest unaccountable power of today [is] the United States and our Western democracies.

[16][17][18] On 24 June 2013, WikiLeaks said that Harrison accompanied Snowden on a high-profile[19] flight from Hong Kong to Moscow en route to political asylum from US extradition.

[2][8][19] Dominic Rushe of The Guardian observed that Harrison was a "strange choice" because of her lack of legal qualifications compared to other WikiLeaks staff, such as human rights lawyer Jennifer Robinson.