> My advice is do not bother.
Second this motion. The number of vendors or administrators who respond well to security or privacy reports is tiny.
Some approximate data from my own emails. I've reported just over 120 security or privacy bugs over the past 4-5 years that this email address goes back (using my real name). I tag the emails, but searching "from:me vulnerability" brings them up. It is like a scoreboard of horrible vendors and site administrators.
From the most recent 100, there are around 25 with no reply at all. I know that some of those, such as government sites were followed up on the phone. Of those with a "(1)" in the thread meaning an additional message, most are me sending a reminder or trying to work out who to contact.
There are then a group of replies where they confirm receipt of the email, but then never confirm the actual contents of what i've reported. Scanning the threads, this looks like another 30 or so emails.
Then there is the group who confirm or deny the bug or parts but get into prolonged technical arguments, with around a dozen threads stretching beyond 10+ emails into arguments about if it is a bug or not.
Last group is those who get the bugs fixed and respond well. In these cases there are only a very small number where the threads are short - most involve long conversations. Some of these are still open - I just reminded myself that I have an open privacy issue with a large web company that still hasn't been fixed. That thread is 30+ emails long.
Overall more than half either didn't reply or didn't confirm the bug (silently fixed or not). There is a messy middle full of long threads and replies that are full of frustration and then only a tiny number of reports where they just get fixed with minimal effort (and you know who these companies are).
There is not a single instance of a non-software company responding well to a bug report (usually from a custom web app), and that includes some well known brands (banks, etc.). The number of good experiences I could count on one hand.
In terms of vendors, recent examples are a 20+ email thread over 3 weeks debating a vendor about severity of a group of bugs (still ongoing), two reasonably well-known vendors with no reply and a well-known vendor who only fixed after more than a month.
You can work out before reporting an issue who the good vendors are. They have a page dedicated to security with contact info, a key and a proper reporting program (preferably with a bounty). With everyone else, you are working for free, wasting your time, not making the internet any more secure and run the risk of getting into trouble - in some countries that could involve legal trouble (there have been a number of raids as a result of security reports in Australia, and the government head of privacy here said there is no such things as a white hat report).