Aloha,

Summary
Dropbox Installer for Windows contains a DLL hijacking vulnerability that
could allow an unauthenticated, remote attacker to execute arbitrary code
on the targeted system. The vulnerability exists due to some DLL file is
loaded by 'DropboxInstaller.exe' improperly. And it allows an attacker to
load this DLL file of the attackeras choosing that could execute arbitrary
code without the user's knowledge.

Affected Product: Dropbox 6.4.14 and prior versions

Tested on: Windows 7

Impact
Attacker can exploit this vulnerability to load a DLL file of the
attacker's choosing that could execute arbitrary code. This may help
attacker to Successful exploit the system if user creates shell as a DLL.

Vulnerability Scoring Details
The vulnerability classification has been performed by using the CVSSv2
scoring system (http://www.first.org/cvss/
<https://hackerone.com/redirect?signature=273a575a933df15fb4c18a77b13c0f4949de2011&url=http%3A%2F%2Fwww.first.org%2Fcvss%2F>
).
Base Score: 7.2 (AV:L/AC:L/Au:N/C:C/I:C/A:C)

More Details:
For software downloaded with a web browser the application directory is
typically the user's "Downloads" directory: see
https://insights.sei.cmu.edu/cert/2008/09/carpet-bombing-and-directory-poisoning.html
<https://hackerone.com/redirect?signature=21fd84ec7a888f372e2663aeb1ea24c253da2958&url=https%3A%2F%2Finsights.sei.cmu.edu%2Fcert%2F2008%2F09%2Fcarpet-bombing-and-directory-poisoning.html>
,
http://blog.acrossecurity.com/2012/02/downloads-folder-binary-planting.html
<https://hackerone.com/redirect?signature=8e7de715fadc691b5fbc9d46f8bc6b0def63a540&url=http%3A%2F%2Fblog.acrossecurity.com%2F2012%2F02%2Fdownloads-folder-binary-planting.html>
and http://seclists.org/fulldisclosure/2012/Aug/134
<https://hackerone.com/redirect?signature=a86c271e4c4a984723abef934bc5f94125458dc6&url=http%3A%2F%2Fseclists.org%2Ffulldisclosure%2F2012%2FAug%2F134>
for
"prior art" about this well-known and well-documented vulnerability.

If an attacker places malicious DLL in the user's "Downloads" directory
(for example per "drive-by download" or "social engineering") this
vulnerability becomes a remote code execution.

Proof of concept/demonstration:
1. Create a malicious PGPmapih.dll file and save it in your "Downloads"
directory.

2. Download 'DropboxInstaller.exe' from https://www.dropbox.com/downloading
and save it in your "Downloads" directory.

3. Execute .exe from your "Downloads" directory.

4. Malicious dll file gets executed.

Informed Vendor: Yes
Fixed Version: TBA

Please assign a CVE ID.

Chao!!
Himanshu Mehta