Yes, Russia has used anthrax in the past. Anthrax is a deadly infectious disease caused by the bacterium Bacillus anthracis, and is found naturally in soil and commonly affects domestic and wild animals. It can also be used as a biological weapon, as was the case in Russia.
In April 1979, an accidental release of anthrax from a military laboratory in Sverdlovsk (now Yekaterinburg) killed at least 66 people and infected many more. The Soviet Union initially denied that the outbreak was due to anthrax, claiming it was due to contaminated meat. However, it was later revealed that a military facility had been conducting research on anthrax as a biological weapon, and that the release was likely due to an accident at the site.
After the fall of the Soviet Union, Russian officials acknowledged that the 1979 outbreak was due to anthrax, and that the Soviet Union had in fact been developing and stockpiling the bacteria as a biological weapon since the 1940s. In 1992, the Russian government declared that it would abide by a global ban on biological weapons and destroyed its stockpile of anthrax.
Despite this, there are still concerns about the potential use of anthrax as a weapon by Russia. In 2018, the US government imposed sanctions on Russian individuals and organizations for their involvement in the production and use of a nerve agent, a type of chemical weapon, in the UK. It is feared that the Russians may have access to and be willing to use biological weapons such as anthrax as well.