TYPO3 Core

Loading a module can cause a strange second HTTP request to the same module. This happens not only when clicking on an entry in the menu but also on drag'n'drop actions.

E.g.: If I call Web>Page, the file alt_db_navframe.php is called twice with identical parameters; if I call one of our extensions in development, mod1/index.php is called twice. The second call has the first one as referer, but we were not able to find the lines of code that trigger that call.

This effect does not seem to do any harm to the Web>Page module, because the call of alt_db_navframe results only in information. Unfortunately, due to drag'n'drop actions, this behaviour results in very bad side effects, because some operations are done twice, which leads to errors.

The browser in use is Mozilla Firefox 1.5.0.3.

The first request header contains the line "Accept: text/xml,application/xml,..."; the second one only "Accept: image/png,*/*". The second call has "If-modified-since" option set in the header, but this might be browser specific.

Only the first call seems to return data, the second GET never had a "HTTP OK" after.

Not all modules showed this behaviour: The user's task center did not produce two http requests.

The problem was introduced in Version 4.0, it was not find in 3.8.1.
(issue imported from #M3435)