Lab: Exploiting blind XXE to retrieve data via error messages
Summary: PortSwigger's lab presents a stock-check feature that parses XML input but does not display the result. The exercise is solved by hosting a malicious external DTD on a separate exploit server, which reads the contents of /etc/passwd into a file entity and then uses that entity in a file path so an error message returns the file's contents.
Bottom line: The data never appears in a normal response - it leaks through an error message, so a parser that fails loudly on attacker-supplied XML can hand over /etc/passwd without any visible output channel.
Read the original at PortSwigger Research ↗
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