As of my last update in September 2021, the latest available data on child slavery came from a 2017 global estimate by the International Labour Organization (ILO) and UNICEF, which estimated that there were 152 million children aged 5 to 17 in forced labor worldwide. This number includes both children in modern slavery, such as forced labor, debt bondage, and child sexual exploitation, as well as children in hazardous work that is considered unacceptable under international standards.
Unfortunately, due to the hidden and illegal nature of child labor and slavery, it is difficult to obtain precise and up-to-date figures. The situation may have changed since then, and it's important to note that these numbers are likely an underestimation of the true magnitude of the issue. To obtain the most current information, I recommend checking reputable sources such as the ILO, UNICEF, or other international organizations working to combat child slavery.