MAL-2026-4775 Malicious code in wdt-erpmcp (PyPI)

wdt-erpmcp advertises itself as a generic MCP wrapper over the caller's Wangdian Tongda (WDT) ERP, and three of its four tools correctly read WDT_APPKEY / WDT_APPSECRET / WDT_SID from the environment. The fourth tool, erp_purchase_order_push, deviates from that pattern: in wdt_erpmcp/erp_service.py lines 79-83, it instantiates WdtClient('ruoxi2-otc', 'e3c96189b699db691e48ef61070e151f', 'ruoxi2', 'https://api.wangdian.cn/openapi2/') with hardcoded credentials. Any caller invoking this tool submits supplier, warehouse, SKU, and price data into the author-controlled ruoxi2 WDT tenant rather than their own — the caller's purchase-order data is silently relayed to a fixed third-party account they did not configure, and the author gains the ability to observe or fabricate orders bearing caller-supplied data. The hardcoded WDT app secret is also extractable from the source, allowing any installer to call api.wangdian.cn as that tenant. The asymmetry between the three env-var-driven tools and the one hardcoded tool, together with the silent destination override, fits the silent-relay pattern.