Nowadays, mobile apps have greatly facilitated our daily work and lives. They are often designed to work closely and interact with each other through app components for data and functionality sharing. The security of app components has been extensively studied and various component attacks have been proposed. Meanwhile, Android system vendors and app developers have introduced a series of defense measures to mitigate these security threats. However, we have discovered that as apps evolve and develop, existing app component defenses have become inadequate to address the emerging security requirements. This latency in adaptation has given rise to the feasibility of cross-layer exploitation, where attackers can indirectly manipulate app internal functionalities by polluting their dependent data. To assess the security risks of cross-layer exploitation in real-world apps, we design and implement a novel vulnerability analysis approach, called CLDroid, which addresses two non-trivial challenges. Our experiments revealed that 1,215 (8.8%) popular apps are potentially vulnerable to cross-layer exploitation, with a total of more than 18 billion installs. We verified that through cross-layer exploitation, an unprivileged app could achieve various severe security consequences, such as arbitrary code execution, click hijacking, content spoofing, and persistent DoS. We ethically reported verified vulnerabilities to the developers, who acknowledged and rewarded us with bug bounties. As a result, 56 CVE IDs have been assigned, with 22 of them rated as ‘critical’ or ‘high’ severity.