SECURE CROSS-ACCOUNT ACCESS IS TRICKY. FOUR COMMON DANGEROUS MISCONCEPTIONS

Summary from the TLDR InfoSec newsletter

IAM role trust policies are the best-practice foundation for cross-account access. However, many users misunderstand the security implications associated with them. When creating role trust policies, users should keep in mind the risk of lateral movement in both their account and the account that they're trusting and therefore be aware that other principals could potentially use the role then those specified in the policy and could potentially gain access to other roles that the policy is not applied to. Many users also mistake the security importance of the management/payer account and allow trust policies to flow between less secure and more secure accounts within an organization.