Even for the good cause breaking is breaking, as long as it is deliberate. And none is obliged to be audited without consent, but in cases (and by actors) defined by law.
What if, for example, your SQL injection has some side effects you didn't expect and damages the audited system? Or what if your SQL injection fails (which is good) but triggers some legal action against you as it is spotted by the admin in the website's log file?
I would therefore strongly advise not going that route. However, why not asking admins before doing, explaining exactly what you explained in this post? Most will say no, but a few might say yes.