the problem comes from the url decode done before the split of the parameters and not after. This patch also implements a less hacky solution for bugs 52491 and 54055 See test case for detail
PR https://github.com/apache/jmeter/pull/98
*** This bug has been marked as a duplicate of bug 58413 ***
This issue has been migrated to GitHub: https://github.com/apache/jmeter/issues/3815