Description
Manipulating classpath asset file URLs, an attacker could guess the path to a known file in the classpath and have it downloaded. If the attacker found the file with the value of the tapestry.hmac-passphrase configuration symbol, most probably the webapp's AppModule class, the value of this symbol could be used to craft a Java deserialization attack, thus running malicious injected Java code. The vector would be the t:formdata parameter from the Form component.
Remediation
References
http://www.openwall.com/lists/oss-security/2021/04/15/1
https://lists.apache.org/thread.html/5173c4eed06e2fca6fd5576ed723ff6bb1711738ec515cb51a04ab24%40%3Cusers.tapestry.apache.org%3E
https://lists.apache.org/thread.html/a4092cb3bacb143571024e79c0016c039b6c982423daa33a7a5c794a%40%3Cusers.tapestry.apache.org%3E
https://lists.apache.org/thread.html/6c40c1e03d2131119f9b77882431a0050f02bf9cae9ee48b84d012df%40%3Cusers.tapestry.apache.org%3E
https://lists.apache.org/thread.html/r87523dd07886223aa086edc25fe9b8ddb9c1090f7db25b068dc30843%40%3Ccommits.tapestry.apache.org%3E
https://lists.apache.org/thread.html/r7d9c54beb1dc97dcccc58d9b5d31f0f7166f9a25ad1beba5f8091e0c%40%3Ccommits.tapestry.apache.org%3E
https://lists.apache.org/thread.html/r237ff7f286bda31682c254550c1ebf92b0ec61329b32fbeb2d1c8751%40%3Cusers.tapestry.apache.org%3E