The scientific library versions prior to 0.3.9.0 had a performance issue in encoding numbers with large coefficients, causing encoding time to be quadratic in the number of digits. This could lead to denial-of-service (DoS) risks in applications that re-encode untrusted JSON numbers, such as proxies or API gateways using aeson. The issue was fixed in version 0.3.9.0 by reimplementing digit extraction to be practically linear, with a recommendation to upgrade to 0.3.10.0 or later to avoid a regression introduced in 0.3.9.0.