Is it permissible for an employee to read topics published anonymously on forums that accuse their company and its managers of corruption, out of fear of falling into backbiting or espionage, and is there any sin upon them for following these topics daily?

If the aforementioned individuals are not known for corruption and openly committing sins, then it is not permissible to delve into their honor or expose their hidden matters. The duty is to offer advice and conceal their faults. Reading what is published about them is considered backbiting (gheeba) or slander (buhtan), both of which are forbidden, unless reading it leads to a benefit or not being aware of it leads to harm for you as an employee in the company. In such cases, it is permissible to read as much as needed, and you must then advise them and clarify the errors that are published about them.