Ericsson is one of the world's biggest telecoms companies and a key player in the rollout of 5G networks in the UK, having replaced Chinese telecoms firm Huawei after security concerns.
The latest revelations follow last week's admission by Ercisson Chief executive Borje Ekholm - in response to the leaked document - that money had been paid by the company to access quicker transport routes in Iraq at the time, and that IS may have been the recipients. More than $5bn was wiped from Ericsson's market value after Mr Ekholm's comments.
The document, obtained by the International Consortium of International Journalists [ICIJ] and shared with the BBC and 29 other media partners, is from a 2019 internal investigation into corrupt activities and bribery in 10 countries. The most serious findings centred on its operations in Iraq.
When IS seized Iraq's second-city, Mosul, in June 2014, a senior Ericsson lawyer recommended shutting down the company's operation in Iraq, but senior managers ignored this, the report found. They felt such an action was "premature", and would "destroy" Ericsson's business in the country, the document says.
Its insistence that the company's contractors continued to work in IS-held territory put lives at risk because the militant group then took a number of contractors hostage, the report found.
Affan was among a group of engineers doing fieldwork for Ericsson at the time IS took over the city. He was sent with a letter on behalf of the company seeking permission from the terror group for them to continue working there.
But as soon as he arrived, they were met by a pick-up truck full of gunmen who seized him, he told German public broadcaster NDR, another of ICIJ's media partners.
Then an IS fighter used his phone to call Ericsson managers and demanded the company pay $2.4m to work in the area, he says.